We first met these four living creatures in Revelation 4:6–9, where they are angelic beings who serve as a guard around the throne of God. They never cease to sing their songs of praise to God (Revelation 4:8–9) and to worship the Lamb (Revelation 5:8).
1 Now I watched when the Lamb opened one of the seven seals, and I heard one of the four living creatures say with a voice like thunder, “Come!”