Three types of amazing 'heavenly beings' are described in the Bible. They don't sound like anything that we'd normally think of as 'angels'!
Seraphim or Seraphs
The word Seraphim (one seraph, two or more seraphim) means “burning ones” or nobles. They are also sometimes called the 'ones of love' because their name might come from the Hebrew root for 'love'. Seraphim are only fully described in the Bible on one occasion. This is in the book of the prophet Isaiah, when he is being commissioned by God to be a prophet and he has a vision of heaven 1.
1 In the year that King Uzziah died, I saw the Lord seated on a throne, high and exalted, and the train of his robe filled the temple.
2 Above him were seraphs, each with six wings: With two wings they covered their faces, with two they covered their feet, and with two they were flying.
3 And they were calling to one another:
"Holy, holy, holy is the LORD Almighty; the whole earth is full of his glory."
4 At the sound of their voices the doorposts and thresholds shook and the temple was filled with smoke.
5 "Woe to me!" I cried. "I am ruined! For I am a man of unclean lips, and I live among a people of unclean lips, and my eyes have seen the King, the LORD Almighty."
6 Then one of the seraphs flew to me with a live coal in his hand, which he had taken with tongs from the altar.
7 With it he touched my mouth and said, "See, this has touched your lips; your guilt is taken away and your sin atoned for."
So these types of heavenly beings have six wings, but they only use two of them for flying. It sounds strange to use wings to cover your face and feet. They may well cover their face because, being so close to God, they would witness His full glory which would be too powerful to behold. Feet are considered 'unclean' and so not worthy to be shown to God. (Some scholars also think that 'feet' could actually mean 'genitals'.) We're not told how many Seraphim there are, but it's more than one.
Their position is flying above God's throne, unlike the Cherubim who are beside/around it. Their primary duty is to constantly glorify and praise God and they may also be the personal 'attendant' angels of God. Their eternal song "Holy, holy, holy is the LORD Almighty; the whole earth is full of his glory." has been used by Jews and Christians for thousands of years to join with the angels in praising God. In Hebrew, to use the same word three times to describe something means that the person/object is utterly like the word. So calling God Holy three times means that God is utterly and perfectly holy.
In Jewish folklore, and some later Christian works, the Seraphim are said to be the highest rank of angel. This is probably because of their very close proximity to God.
In art, Seraphim are often red (because of their names 'burning ones') and are shown holding a flaming sword with the words 'holy, holy, holy' on the blade.
The coal in Isaiah's vision, that touches his lips, is used to signify that Isaiah is now purified and fit to be a prophet. The coal came from the altar in heaven, so would have been very powerful. Fire is also used in many religions and faiths as a way of purifying and cleansing something.
Cherubim or Cherubs
When most people think of Cherubs they'll think of pudgy little baby-like creatures, with two little wings, who are rather cute. However, that's not how the Bible describes them! Cherubs (the correct pural is Cherubim) are described in two books of the Bible, Genesis and Ezekiel (a Jewish prophet).
In Genesis they guard the Garden of Eden, following Adam and Eve's banishment from the Garden, and are described holding flaming swords 2.
After he [God] drove the man out, he placed on the east side of the Garden of Eden cherubim and a flaming sword flashing back and forth to guard the way to the tree of life.
The prophet Ezekiel has a vivid vision of heaven where he sees many angelic beings. His description of the Cherubim is powerful – almost frightening 3.
1 In the thirtieth year, in the fourth month on the fifth day, while I was among the exiles by the Kebar River, the heavens were opened and I saw visions
2 On the fifth of the month--it was the fifth year of the exile of King Jehoiachin-- 3 the word of the LORD came to Ezekiel the priest, the son of Buzi, by the Kebar River in the land of the Babylonians. There the hand of the LORD was upon him.
4 I looked, and I saw a windstorm coming out of the north--an immense cloud with flashing lightning and surrounded by brilliant light. The center of the fire looked like glowing metal,
5 and in the fire was what looked like four living creatures. In appearance their form was that of a man,
6 but each of them had four faces and four wings.
7 Their legs were straight; their feet were like those of a calf and gleamed like burnished bronze.
8 Under their wings on their four sides they had the hands of a man. All four of them had faces and wings,
9 and their wings touched one another. Each one went straight ahead; they did not turn as they moved.
10 Their faces looked like this: Each of the four had the face of a man, and on the right side each had the face of a lion, and on the left the face of an ox; each also had the face of an eagle.
11 Such were their faces. Their wings were spread out upward; each had two wings, one touching the wing of another creature on either side, and two wings covering its body.
12 Each one went straight ahead. Wherever the spirit would go, they would go, without turning as they went.
13 The appearance of the living creatures was like burning coals of fire or like torches. Fire moved back and forth among the creatures; it was bright, and lightning flashed out of it. 14 The creatures sped back and forth like flashes of lightning.
Ezekiel 1: 1-14
22 Spread out above the heads of the living creatures was what looked like an
expanse, sparkling like ice, and awesome.
23 Under the expanse their wings were stretched out one toward the other, and each had two wings covering its body.
24 When the creatures moved, I heard the sound of their wings, like the roar of rushing waters, like the voice of the Almighty, like the tumult of an army. When they stood still, they lowered their wings.
3 Now the cherubim were standing on the south side of the temple when the man went in, and a cloud filled the inner court.
4 Then the glory of the LORD rose from above the cherubim and moved to the threshold of the temple. The cloud filled the temple, and the court was full of the radiance of the glory of the LORD.
5 The sound of the wings of the cherubim could be heard as far away as the outer court, like the voice of God Almighty when he speaks.
6 When the LORD commanded the man in linen, "Take fire from among the wheels, from among the cherubim," the man went in and stood beside a wheel.
7 Then one of the cherubim reached out his hand to the fire that was among them. He took up some of it and put it into the hands of the man in linen, who took it and went out.
8 (Under the wings of the cherubim could be seen what looked like the hands of a man.)
Their entire bodies, including their backs, their hands and their wings, were completely full of eyes ...
Each of the cherubim had four faces: One face was that of a cherub, the second the face of a man, the third the face of a lion, and the fourth the face of an eagle.
20 These were the living creatures I had seen beneath the God of Israel by the Kebar River, and I realized that they were cherubim.
21 Each had four faces and four wings, and under their wings was what looked like the hands of a man.
22 Their faces had the same appearance as those I had seen by the Kebar River. Each one went straight ahead
Not your average cute little angel! These are powerful heavenly beings with four faces and four wings.
The Cherubim are also described in the construction of the 'Ark of the Covenant'. (Yes, the one out of the Indiana Jones film!) The Ark was the dwelling place of God with the Israelites during their exodus in the desert 4.
17 "Make an atonement cover of pure gold--two and a half cubits long and a cubit and a half wide.
18 And make two cherubim out of hammered gold at the ends of the cover.
19 Make one cherub on one end and the second cherub on the other; make the cherubim of one piece with the cover, at the two ends.
20 The cherubim are to have their wings spread upward, overshadowing the cover with them. The cherubim are to face each other, looking toward the cover.
21 Place the cover on top of the ark and put in the ark the Testimony, which I will give you.
22 There, above the cover between the two cherubim that are over the ark of the Testimony, I will meet with you and give you all my commands for the Israelites.
The ark was placed in the Jewish Temple, when it was built in Jerusalem. The holy part of the Temple (where the ark was placed and where the highest alter was located) also featured statues of Cherubim 5.
23 In the inner sanctuary he made a pair of cherubim of olive wood, each ten cubits high [about 15 ft / 4.5 metres].
24 One wing of the first cherub was five cubits long, and the other wing five cubits--ten cubits from wing tip to wing tip.
25 The second cherub also measured ten cubits, for the two cherubim were identical in size and shape.
26 The height of each cherub was ten cubits.
27 He placed the cherubim inside the innermost room of the temple, with their wings spread out. The wing of one cherub touched one wall, while the wing of the other touched the other wall, and their wings touched each other in the middle of the room.
28 He overlaid the cherubim with gold.
1 Kings 6:23-28
6 The priests then brought the ark of the LORD's covenant to its place in the inner sanctuary of the temple, the Most Holy Place, and put it beneath the wings of the cherubim.
7 The cherubim spread their wings over the place of the ark and overshadowed the ark and its carrying poles.
1 Kings 8:6-7
In Ezekiel's vision he also describes another type of angelic beings that seem to be associated with the Cherubim. Their description is even more strange, to our eyes 6.
15 As I looked at the living creatures, I saw a wheel on the ground beside each creature with its four faces.
16 This was the appearance and structure of the wheels: They sparkled like chrysolite, and all four looked alike. Each appeared to be made like a wheel intersecting a wheel.
17 As they moved, they would go in any one of the four directions the creatures faced; the wheels did not turn about as the creatures went.
18 Their rims were high and awesome, and all four rims were full of eyes all around.
19 When the living creatures moved, the wheels beside them moved; and when the living creatures rose from the ground, the wheels also rose.
20 Wherever the spirit would go, they would go, and the wheels would rise along with them, because the spirit of the living creatures was in the wheels.
21 When the creatures moved, they also moved; when the creatures stood still, they also stood still; and when the creatures rose from the ground, the wheels rose along with them, because the spirit of the living creatures was in the wheels.
9 I looked, and I saw beside the cherubim four wheels, one beside each of the cherubim; the wheels sparkled like chrysolite.
10 As for their appearance, the four of them looked alike; each was like a wheel intersecting a wheel.
11 As they moved, they would go in any one of the four directions the cherubim faced; the wheels did not turn about as the cherubim went. The cherubim went in whatever direction the head faced, without turning as they went.
12 Their entire bodies, including their backs, their hands and their wings, were completely full of eyes, as were their four wheels.
13 I heard the wheels being called "the whirling wheels."
15 Then the cherubim rose upward. These were the living creatures I had seen by the Kebar River.
16 When the cherubim moved, the wheels beside them moved; and when the cherubim spread their wings to rise from the ground, the wheels did not leave their side.
17 When the cherubim stood still, they also stood still; and when the cherubim rose, they rose with them, because the spirit of the living creatures was in them.
18 Then the glory of the LORD departed from over the threshold of the temple and stopped above the cherubim.
19 While I watched, the cherubim spread their wings and rose from the ground, and as they went, the wheels went with them. They stopped at the entrance to the east gate of the LORD's house, and the glory of the God of Israel was above them.
Certainly an amazing scene. Ezekiel's vision might seems strange, it might well be that human eyes and senses just can't properly describe the wonder of heaven.
The Bible doesn't say how many Cherubim there are, but we're told that Ezekiel saw four - and there may be more than that! Their role is to guard God's Holy domain and presence from any sin and corruption. They are sometime known as the throne angels as they are seen to be around the throne of God 7.
Hear us, O Shepherd of Israel, you who lead Joseph like a flock; you who sit
enthroned between the cherubim ...
The LORD reigns, let the nations tremble; he sits enthroned between the cherubim, let the earth shake.
In Jewish folklore the 'Throne Angels' are known as Merkabah.
Having four faces on four side of their heads and being arranged in a square, they can travel in any direction without having to turn.
The word Cherub may come from a term 'to guard' which would fit well with their role. No where in the Bible are the Cherubim directly called angels!
So far from being cute, cuddly creatures, the Cherubim are the mighty and powerful guardians of God.
The Four Living Creatures
In the final book of the Bible, Revelation, there's a description of 'Four Living Creatures' 8.
6 In the center, around the throne, were four living creatures, and they were covered with eyes, in front and in back.
7 The first living creature was like a lion, the second was like an ox, the third had a face like a man, the fourth was like a flying eagle.
8 Each of the four living creatures had six wings and was covered with eyes all around, even under his wings. Day and night they never stop saying:
"Holy, holy, holy is the Lord God Almighty, who was, and is, and is to come."
9 Whenever the living creatures give glory, honor and thanks to him who sits on the throne and who lives for ever and ever,
10 the twenty-four elders fall down before him who sits on the throne, and worship him who lives for ever and ever.
These amazing creatures have features in common with both the Seraphim, in having six wings and continually praising God; and like the Cherubim, that they number four, are covered in eyes and look like a lion, ox, man and eagle.
Whether these creatures are Seraphim, Cherubim or another sort of angelic/heavenly being, we simply don't know. But they are certainly amazing and very powerful.