Bible Notes Online - Revelation 15 - ESV
Commentary

v1: Seven angels with seven last plagues, the seven bowls; in this the wrath of God is complete.

v2-4: Those who follow Jesus Christ enjoy victory over the beast; their reliance is on the Lord God Almighty. Their song is centred on God and His character, not on their own achievements.

John seems to refer to Jer 10.7, "Who should not revere you, O King of hte nations!" John tries to find words to express his response to what he sees, this "great and marvellous sign."  As we face any situation, we do well to let the Bible speak to us, to gives us thoughts and words to inform and mould our responses, our opinions, our words, our actions.

v5: See also 11.19, the temple, or tabernacle, in Heaven is opened. This introduces the bowls of God's wrath.

v6-8: The seven final plagues come from the temple of God; He does send His judgment upon the earth. This reflects His perfect, righteous character, and so the angels are dressed in pure bright linen. By these plagues, the out-pouring of God's wrath on the earth is completed.