What does Revelation 1:6 mean?

Once we were helpless sinners, but now, as John explains in this verse, we are a royal priesthood (1 Peter 2:9). Once we served sin; now we worship and serve God. We are a kingdom of priests. In Old Testament times, priests offered sacrifices on behalf of the people of Israel and stood as mediators between the people and God. Now we come directly to God through Jesus, and we offer ourselves and spiritual sacrifices to God (Romans 12:1; 1 Peter 2:5). Once we were in Satan's domain; now we are in Jesus' domain. Ephesians 2:2, 5 remind us that once we were followers of the prince of the power of the air—Satan—but our merciful and loving God made us alive together with Christ.

As John contemplates what God has done for believers by making us a kingdom and priests, he spontaneously offers praise to God. He ascribes glory and dominion. He concludes his doxology by saying, "Amen," meaning, "Let it be so!" A similar praise for God's grace and power on our behalf should arise from our hearts and lips.