John classified the Book of Revelation as a "prophecy" (Rev 1:3). We are to "heed the things which are written in it; for the time is near" (:3). Revelation 20:6 speaks of the "first resurrection" which takes place after the events of the Great Tribulation. Satan is bound "for a thousand years" (20:2). Martyrs "came to life and reigned with Christ for a thousand years" (:4) and "the rest of the dead did not come to life until the thousand years were completed" (:5). John "saw thrones, and they sat upon them, and judgment was given to them" (:4) and they "will reign with Him for a thousand years" (:6). If you are a premillennialist you expect prophecy to predict literal events. A specific measure of time could be figurative as long as it doesn't originate exclusively in man's imagination. But proper exegesis requires a literal interpretation if possible. "'Nothing will be impossible with God'" (Lk 1:37).
In a sense, what God does is timeless. "Thou didst give birth to the earth and the world, even from everlasting to everlasting, Thou are God" (Ps 90:2). The phrase '1000 years' is mentioned five times in the first six verses of chapter twenty. Premillennialists say that a literal interpretation would be consistent with other OT and NT references to God's promises. Nonetheless, the number one-thousand is composed of the number ten multiplied by itself three times. Repetition demonstrates the importance of something. Also, the number carries a Biblical meaning depending on how it is consistently used in the Bible. "10" indicates completeness as in the Ten Commandments or the ten plagues of Egypt. There is an orderly completion of a cycle where nothing is lacking. "10" also indicates trials and testings. Israel tested God ten times (Nu 14:22), prisoners were tested ten days (Rev 2:10), and Abraham asked if God would spare Sodom for ten righteous people (Ge 18:32-33).
"A thousand years in Thy sight are like yesterday when it passes by" (:4). Peter discusses the "last days" (2Pe 3:3) where people ask "'Where is the promise of His coming?'" (:4). "He has made everything appropriate in its time" (Ecc 3:11). "It escapes their notice that by the word of God the heavens existed long ago" (2Pe 3:5). Peter reminds them to notice that "with the Lord one day is as a thousand years" (:8). It could represent a complete long period of indeterminate length. But there is also a definite schedule because "the Lord is not slow about His promise" (:9). "'That day and hour no one knows . . . but the Father alone'" (Mt 24:36).
Revelation 20:1-6 presents the millennium and you can't dismiss it's validity just because of it's brief mention. Speaking in tongues and the Lord's table are explained only once in New Testament epistles. It is a time of peace because Satan is bound for a thousand years (:2). It is a period of theocratic government because they reigned with Christ for a thousand years (:4,6). Jesus said, "'In the regeneration when the Son of Man will sit on His glorious throne, you also shall sit upon twelve thrones, judging the twelve tribes of Israel'" (Mt 19:28). John saw "thrones and they that sat upon them, and judgment was given to them" (Rev 20:4). "In the last days, the mountain of the house of the Lord will be established as the chief of the mountains . . . and all the nations will stream to it" (Isa 2:2). "Behold, the Lord God will come with might, with His arm ruling for Him" (40:10). "The Lord has established His throne in the heavens; and His sovereignty rules over all" (Ps 103:19). "Thy kingdom is an everlasting kingdom, and Thy dominion endures throughout all generations" (145:13). In the millennium (and afterwards) you could say that Christ fulfills the functions of the executive, legislative, and judicial functions of government. "For the Lord is our judge, the Lord is our lawgiver, the Lord is our King" (33:22).
The Messianic kingdom was prophesied with, "'Your house and your kingdom shall endure before Me forever; your throne shall be established forever'" (2Sa 7:16). "There will be no end to the increase of His government or of peace; on the throne of David and over his kingdom" (Isa 9:7). It is because "a Son will be given to us; and the government will rest on His shoulders" (:6). It is a matter of authority, power, dominion and rule. "For the kingdom is the Lord's, and He rules over the nations" (Ps 22:28). "The Spirit of the Lord God is upon me" (Isa 61:1) "to proclaim the favorable year of the Lord, and the day of vengeance of our God" (:2). "His dominion will be from sea to sea, and from the River to the ends of the earth" (Zec 9:10). "He will judge between the nations, and will render decisions for many peoples" (Isa 2:4). "With righteousness He will judge the poor, and decide with fairness for the afflicted of the earth" (11:4).
Is the Messianic kingdom synonymous with the millennial kingdom? "For Zion's sake I will not keep silent, and for Jerusalem's sake I will not keep quiet" (Isa 62:1). "The law will go forth from Zion, and the word of the Lord from Jerusalem" (2:3). There is "an inheritance in the kingdom of Christ and God" (Eph 5:5). Jesus' disciples had "'been given the mystery of the kingdom of God'" (Mk 4:11). Jesus preached "'the kingdom of heaven is at hand'" (Mt 4:17). The Pharisees questioned Jesus "as to when the kingdom of God was coming" (Lk 17:20) and he replied "'the kingdom of God is in your midst'" (:21). Eventually, of course, it will be proclaimed, "'The kingdom of the world has become the kingdom of our Lord'" (Rev 11:15). But there was a tension between the current and future realities of the kingdom. Jesus knew this since "they supposed that the kingdom of God was going to appear immediately" (Lk 19:11). Must one wait until the millennium for the kingdom to be fulfilled? We know that scripture teaches that the kingdom is already present because John said he was a "fellow-partaker in the tribulation and kingdom and perseverance which are in Jesus" (Rev 1:9). Paul stated, "He delivered us from the domain of darkness, and translated us to the kingdom of His beloved Son" (Col 1:13). Jesus explained, "'When you see these things happening, recognize that the kingdom of God is near . . . [and] this generation will not pass away until all things take place'" (Lk 21:31-32).