I hold that the millennial reign of Christ is right now as has been since he was resurrected.
He appeared to the disciples in Matthew 28:18 and said:
18 And Jesus came up and spoke to them, saying, All authority has been given to Me in heaven and on earth.
Christ received all authority from God! This is why He reigns now.
In 1 Corinthians 15:20-28 I believe it's pretty clear Christ reigns now:
20 But now Christ has been raised from the dead, the first fruits of those who are asleep.
21 For since by a man came death, by a man also came the resurrection of the dead.
22 For as in Adam all die, so also in Christ all will be made alive.
23 But each in his own order: Christ the first fruits, after that those who are Christs at His coming,
24 then comes the end, when He hands over the kingdom to the God and Father, when He has abolished all rule and all authority and power.
25 For He must reign until He has put all His enemies under His feet.
26 The last enemy that will be abolished is death.
27 For He has put all things in subjection under His feet. But when He says, All things are put in subjection, it is evident that He is excepted who put all things in subjection to Him.
28 When all things are subjected to Him, then the Son Himself also will be subjected to the One who subjected all things to Him, so that God may be all in all.
Christ will deliver the kingdom to God after he returns and judgment has been completed, so the millennial reign is now because clearly at *the end* Christ returns the kingdom to God
The millennial reign is not literal as I view scripture. The 1000 years speaks to the complete time that Christ reigns, and we are in that period as we await His return.
Paul tells us clearly in Ephesians 1:18-23:
18 I pray that the eyes of your heart may be enlightened, so that you will know what is the hope of His calling, what are the riches of the glory of His inheritance in the saints,
19 and what is the surpassing greatness of His power toward us who believe. These are in accordance with the working of the strength of His might
20 which He brought about in Christ, when He raised Him from the dead and seated Him at His right hand in the heavenly places,
21 far above all rule and authority and power and dominion, and every name that is named, not only in this age but also in the one to come.
22 And He put all things in subjection under His feet, and gave Him as head over all things to the church,
23 which is His body, the fullness of Him who fills all in all.
Colossians 1:17-20 clearly states Christ reigns now:
17 He is before all things, and in Him all things hold together.
18 He is also head of the body, the church; and He is the beginning, the firstborn from the dead, so that He Himself will come to have first place in everything.
19 For it was the Fathers good pleasure for all the fullness to dwell in Him, 20 and through Him to reconcile all things to Himself, having made peace through the blood of His cross; through Him, I say, whether things on earth or things in heaven.
Christ reigns now! People want to look at things now and conclude Christ is not reigning, because of how the world is going, but Christ is in control of everything right now. This will continue until the salvation of all to be saved is complete. Christ will then come and judge the world.
As Paul wrote to Timothy he proclaimed Christ reign in 1 Timothy 6:13-16:
13 I charge you in the presence of God, who gives life to all things, and of Christ Jesus, who testified the good confession before Pontius Pilate,
14 that you keep the commandment without stain or reproach until the appearing of our Lord Jesus Christ,
15which He will bring about at the proper timeHe who is the blessed and only Sovereign, the King of kings and Lord of lords,
16 who alone possesses immortality and dwells in unapproachable light, whom no man has seen or can see. To Him be honor and eternal dominion! Amen.
Christ is the ONLY SOVEREIGN right now! He is simply waiting for the "proper time" to exercise judgment....we are in the millennium now!!!