Cherubs are only mentioned a few times in the Bible. In every passage except one they are either sculpted, part of a vision or used metaphorically.
Sculpted cherubs were part of the ark of the covenant. They were made of hammered gold, along with the lid of the ark, called the “mercy seat”.
You shall make a mercy seat of pure gold. Two cubits and a half shall be its length, and a cubit and a half its breadth. And you shall make two cherubim of gold; of hammered work shall you make them, on the two ends of the mercy seat. Make one cherub on the one end, and one cherub on the other end. Of one piece with the mercy seat shall you make the cherubim on its two ends. The cherubim shall spread out their wings above, overshadowing the mercy seat with their wings, their faces one to another; toward the mercy seat shall the faces of the cherubim be.
(Cherubim is the Hebrew plural for cherub.) Solomon also made cherubim for the temple (1 Kings 6:23-28) and there were carved cherubim as part of Ezekiel’s temple (Ezekiel 41:18,20,25).
Cherubim also appeared in visions of Ezekiel.
And I looked, and behold, there were four wheels beside the cherubim, one beside each cherub, and the appearance of the wheels was like sparkling beryl. 10 And as for their appearance, the four had the same likeness, as if a wheel were within a wheel. 11 When they went, they went in any of their four directions without turning as they went, but in whatever direction the front wheel faced, the others followed without turning as they went. 12 And their whole body, their rims, and their spokes, their wings, and the wheels were full of eyes all around—the wheels that the four of them had. 13 As for the wheels, they were called in my hearing “the whirling wheels.” 14 And every one had four faces: the first face was the face of the cherub, and the second face was a human face, and the third the face of a lion, and the fourth the face of an eagle.
15 And the cherubim mounted up. These were the living creatures that I saw by the Chebar canal. 16 And when the cherubim went, the wheels went beside them. And when the cherubim lifted up their wings to mount up from the earth, the wheels did not turn from beside them. 17 When they stood still, these stood still, and when they mounted up, these mounted up with them, for the spirit of the living creatures was in them.
John saw similar creatures in his visions in Revelation 4:6-8, although they are not called cherubim there. Since these were part of a vision, these were probably not real either.
A cherub is used metaphorically in the highly figurative song of David in 2 Samuel 22 which describes God riding on a cherub (2 Samuel 22:11). The surrounding verses also describe God having smoke going up from his nostrils, fire in his mouth, clouds as clothing, and a voice of thunder. So there is no justification to take the reference to the cherub literally.
The only passage where they appear to be real is Genesis 3:24
He drove out the man, and at the east of the garden of Eden he placed the cherubim and a flaming sword that turned every way to guard the way to the tree of life.
However, some people interpret this passage metaphorically also.