The great question of Revelation 20 is whether we are to understand the thousand years as a literal time when Christ is rule over His Jewish kingdom after His second coming.
The binding of Satan (vv. 1-3) is given in such a way to show that we were never meant to understand it literally. How can an angel bind a spiritual being with a literal chain? This vision is intended to demonstrate Christâ€™s victory over Satan at the cross. In Matthew 12:22-32, the Pharisees confronted Jesus over His healing of a demon-possessed man. Jesus testified that he came to bind the strong man in order to spoil his house.
This binding of Satan took place with Christâ€™s first coming and His death on the cross (Gen. 3:15). He will be bound until right before Christâ€™s second coming. At that time Satan will again be able to deceive the nations for a brief time until he is cast into the lake of fire forever.
His binding is for the purpose of restraining his ability to prevent the gospel from being fruitful in bring to Christ an innumerable multitude from every tongue, tribe, family, and nation (Rev. 5:9). Revelation 12 speaks of his being cast out of heaven because, through the blood of Christ, he can no longer accuse the saints before the throne of God.