8:5 And the angel... filled it with the fire of the altar. Fire is usually a symbol of suffering.
And cast [it] into the earth. This fire cast from the altar upon the earth indicates that the judgments of God are about to fall upon it. The earth in the sense used by John is the great Roman Empire, which embraced the civilized world.
And there were voices, and thunderings, and lightnings, and an earthquake. These mutterings and the quakings are ominous of the terrible scenes to follow when the angels sound their trumpets.
8:5 And there were thunderings, and lightnings, and voices, and an earthquake - These, especially when attended with fire, are emblems of God's dreadful judgments, which are immediately to follow.
8:1-6 The seventh seal is opened. There was profound silence in heaven for a space; all was quiet in the church, for whenever the church on earth cries through oppression, that cry reaches up to heaven; or it is a silence of expectation. Trumpets were given to the angels, who were to sound them. The Lord Jesus is the High Priest of the church, having a golden censer, and much incense, fulness of merit in his own glorious person. Would that men studied to know the fulness that is in Christ, and endeavoured to be acquainted with his excellency. Would that they were truly persuaded that Christ has such an office as that of Intercessor, which he now performs with deep sympathy. No prayers, thus recommended, was ever denied hearing and acceptance. These prayers, thus accepted in heaven, produced great changes upon earth. The Christian worship and religion, pure and heavenly in its origin and nature, when sent down to earth and conflicting with the passions and worldly projects of sinful men, produced remarkable tumults, here set forth in prophetical language, as our Lord himself declared, Lu 12:49.