Reference

Revelation 15-16, 11
The Tribulation, Part 3

Revelation 15- Preparations for the Judgments.  As the final judgments are being prepared to be unleashed on the world, there is worship going on in heaven; worship for God, because He is worthy of it.  The song of Moses in Revelation 15:3 is most likely from Ex. 15:1-21; Deut. 32:1-43 and it is a song of redemption.  It declares God to be the Almighty and Righteous King.