Then I saw an angel coming down from heaven, holding in his hand the key to the bottomless pit and a great chain. And he seized the dragon, that ancient serpent, who is the devil and Satan, and bound him for a thousand years, and threw him into the pit, and shut it and sealed it over him, so that he might not deceive the nations any longer, until the thousand years were ended. After that he must be released for a little while. (Revelation 20:1-3, ESV)
Revelation 20 is the great dividing point for interpreters of Revelation. Many believe this passage refers to the period after the second coming of Christ. The reason is that this vision, they would argue, follows in time sequence, the visions of chapter 19. In this view, Satan is not completely defeated, but is bound for a thousand years and is released at the end of the one-thousand years for a great war against Christ and the saints.
A second view is that this passage is a retelling of the history from the time of Christ's ascension into heaven, nearly two-thousand years ago, to the time when Christ will return again in the future.
By far the most popular view for Christians, at least in the United States, is the first view. I hold to the second view for several reasons. First, I see that Revelation has already presented the visions in cycles of retelling, recapitulation, or overlays of visions on the same period of history. Each overlay presents another view of the period of history between Christ's first advent to his second coming. Secondly, there is a complete destruction of the armies in Revelation 19. There does not appear to be anyone left to destroy again, or any seeds left to sprout into those to be destroyed again. Thirdly, in the bowls judgment cycle, a loud voice from the thrown cries out "it is done" at the seventh seal. Another period of a thousand year period which concludes with more fighting of Satan would mean the judgments were not done with the seventh bowl. Fourthly, numbers in Revelation have symbolic meaning just as other symbols in Revelation. The millennium speaks of the mightily reign of Christ and his church. The gospel has gone throughout the world and Satan could not stop it. Finally, I think the rest of scripture presents a clear picture that all of redemptive history completes with Christ's second coming. If we did not have Revelation 20, there would be no speculation about a millennium after Christ's return where there would be a great battle at the end of the millennium.
But those of the first view might ask, If the millennium is now, how was Satan bound? The answer comes from Jesus. He told the Pharisees in Matthew 12:24-29 that he does his work because he has bound the strong man Satan. period Christ also spoke of Satan falling in Luke 10:17-19 when the seventy-two disciples excitedly reported back after Jesus had sent them out ahead of them.
This binding of Satan relates the the gospel going forth to all the nations. Before Christ's first advent, the people who responded to God were largely the Israelites and the Jews. Since Christ's advent, the gospel is going to all the nations.
So, what does this have to do with us? We live in the millennial period where the kingdom of God is spreading to all the nations and people groups. God is powerfully at work. Since we live in the period of God extending his kingdom, we can have the joy of taking part in this. This is not a time to hang back, but a time to celebrate God's millennial rule by participating in it.