Rev 20:1-3    "And I saw an angel come down from heaven, having the key of the bottomless pit and a great chain in his hand. 2 And he laid hold on the dragon, that old serpent, which is the Devil, and Satan, and bound him a thousand years, 3 And cast him into the bottomless pit, and shut him up, and set a seal upon him, that he should deceive the nations no more, till the thousand years should be fulfilled: and after that he must be loosed a little season."

The word, angel, means messenger.  The messenger is the messenger of the covenant as set forth in Mal. 3:1: "Behold, I will send my messenger, and he shall prepare the way before me: and the Lord, whom ye seek, shall suddenly come to his temple, even the messenger of the covenant, whom ye delight in: behold, he shall come, saith the LORD of hosts."  He came down from heaven to do the Father's will.  In Rev. chapter 9 Satan is called the angel of the bottomless pit: 9:11 "And they had a king over them, which is the angel of the bottomless pit, whose name in the Hebrew tongue is Abaddon, but in the Greek tongue hath his name Apollyon."  Thus the messenger of the covenant (Christ) has locked up the messenger of the bottomless pit (Satan) for a thousand years. 

Someone may ask, "If Satan is locked up, then why does he cause me such trouble?"  Satan is not locked up so as not to be able to cause us trouble or to make shipwreck people's lives.  He is not locked up so as not to be able to entice us to sin.  Indeed he causes much havoc in people's lives and in the world.  "How then," we may ask, "is Satan locked up?"  Specifically he is locked up so as to deceive the nations no more until the thousand years should be fulfilled.  If you will recall in chapter 17 we read about the seven heads of the seven headed beast: "10  And there are seven kings: five are fallen, and one is, and the other is not yet come; and when he cometh, he must continue a short space."  The seventh multinational kingdom has not yet arisen to reign over the earth.  Satan has been bound so as not to be able to form this seventh head until the thousand years is fulfilled.  Verse 4 speaks to us about the significance of the thousand years and we will save our comments about the thousand years until we get to verse 4.

The use of the word, chain, is indicative of the bondage that Satan is under.  He is not able to form the seventh kingdom until that chain is removed by the Lord.  Once the chain is removed and God sets that date, then Satan shall go forth to once again deceive the nations into yielding to a multinational one world government.  Perhaps the United Nations is that seventh head, time will tell.

That the Lord has the key to lock and unlock tells us that He has sovereign control over what Satan is allowed to do.  Satan can do no more than what he is allowed to do.  This doesn't mean that God causes Satan to do what he does.  It just means that Satan is limited by God's sovereign control.  Job is a good example of this control that God has over Satan.  Satan could not touch Job so long as God had him hedged in.  Once God removed the hedge then Satan did his damage, but only to the extent that God would allow him.  He couldn't touch Job's life because God restricted him.  Thus Satan cannot form this seventh head until God allows.

Let us not forget that once the thousand years is fulfilled, Satan will be loosed a little season so as to go forth and deceive the nations once again.