Symbolism, Imagery, Allegory
We're not done with this chariot thing yet. Ezekiel doesn't just see a bunch of fluffy critters pulling God's chariot… he sees—well, God. Or, technically, not really, since "no man can see God and live." He sees "appearance the likeness of the glory of God"—a visionary image or representation of God's glory that isn't actually the same thing as God himself. He can't even find the words to explain it. But it might be as close as a mortal like Ezekiel can get without dropping dead on the spot.
Here's the description straight from Ezekiel himself:
And above the dome over their heads there was something like a throne, in appearance like sapphire; and seated above the likeness of a throne was something that seemed like a human form. Upward from what appeared like the loins I saw something like gleaming amber, something that looked like fire enclosed all around; and downward from what looked like the loins I saw something that looked like fire, and there was a splendor all around. Like the bow in a cloud on a rainy day, such was the appearance of the splendor all around. This was the appearance of the likeness of the glory of the Lord. (1:26-28)
Since God himself is beyond representation—which is why he won't let the Israelites worship idols or make images of him—he can only be seen indirectly. God isn't actually a guy with fiery legs surrounded by a rainbow: that's just his costume for this special, prophetic occasion.