I doubt not but by fire here, is to be understood the wrath of God, often in holy writ compared to fire, poured out upon the Roman empire, or the visible church. Upon which followed great judgments, and confusions, and tumults, expressed here, or ushered in, as before, Revelation 6:1, with thunderings; which being here more generally mentioned, are by and by more particularly expressed.
Related Commentaries of Revelation 8:5
Revelation 8:5
5 And the angel took the censer, and filled it with fire of the altar, and cast it intob the earth: and there were voices, and thunderings, and lightnings, and an earthquake.