8:5 And the angel took the censer; and he filled it with the fire of the altar and threw it to the earth; and there followed peals of thunder and sounds and flashes of lightning and an earthquake.

And the ANGEL took the censer;

This is the censer that has the prayers of the saints purified and filtered by the "much incense"

and he filled it with the FIRE of the ALTAR,

It is not clear if there is only one altar in heaven, the incense altar. There is no need for a "sacrifices" alter because the supreme sacrifice has already taken place, Hebrews 12:28-29. This altar is probably the one where the souls are seeking vengeance in Revelation 6:9. This implies the FIRE symbolizes God in His holy and pure judgmental form. We are about to see another side of a loving and caring God.

and threw it to the earth.

See the previous verse for some thoughts on where heaven is. The lull in heaven in verse 1 when the seventh seal was opened may also have been on the earth. If so, that lull is over!

and there followed

This is much like God's visit to Mt. Sinai in Exodus 19:16-20. This is the tribulation saints vindication. Compare the consequences in Hebrews 10:26-31, Luke 12:49-53, and 2 Thessalonians 1:5-10. Note, too, there is no indication that there is any rain. This implies the fire continues on for some time, perhaps for the duration of the seven trumpets.