The Millennium is this enigmatic, mystifying period preceding judgment and the eternal state.
This is a period of vindication within history of the cause of Yahusha.
There will be two tribulation periods (Jacob's Trouble and the Gt. Tribulation) and with that two categories of resurrection of the dead.
The first resurrection is the resurrection of the believers who did not worship the beast or receive its mark - Revelation 20:4-5 who gain entrance into “the Millennium” (some limit the Millennium to the martyrs alone - Rev 6). I disagree with this limited view though I recognize however a connection in Matt 10:39, “whoever looses his life for my sake, will find it.” but don’t limit it to just that. In this teaching find out about a literal thousand year reign here on earth administered under the Melchizedik Priesthood and its Shavuot inception point - the Book of the Covenant - Exo. 24.7.