John sees four living creatures in the midst of and around the Lord’s throne. They are the cherubim who form the throne (Revelation 4:6b-7).
They are full of eyes, so they can look every which way as they guard the holiness of the Lord’s presence (v. 6b). But we never see them looking at anything. Instead, these eye-filled creatures speak and sing (4:8; 5:8-9).
They guard not with their eyes but with their mouths. They guard by praise.
It is not only the creatures as such who form the throne, but creatures-praising. The Lord is enthroned on their praises.