Albert Barnes Commentary 1 Chronicles 28:18

"and for the altar of incense refined gold by weight; and gold for the pattern of the chariot, [even] the cherubim, that spread out [their wings], and covered the ark of the covenant of Jehovah." — 1 Chronicles 28:18 (ASV)

The chariot of the cherubim - The cherubim are themselves the chariot upon which Yahweh rides (Psalms 18:10; Psalms 99:1).