Revelation 20:5-6 But the rest of the dead did not live again until the thousand years were finished. This is the first resurrection. Blessed and holy is he who has part in the first resurrection. Over such the second death has no power, but they shall be priests of God and of Christ, and shall reign with Him a thousand years.

Some die with Christ as Savior and some do not.
All that die in Christ take part in the first resurrection.
First is not a number, in this case, it is the raising of the dead in Christ.
The first resurrection is to eternal life.
1 Cor 15:20 says that Christ is risen from the dead, and has become the firstfruits of those who have fallen asleep.
Jesus is the First Resurrection!
If the first resurrection were a number then the Bible would mention a second resurrection but it does not.
It does mention a second death.
As someone once said, “You can be born twice and die once or you can be born once and die twice!”
The second death has no power over those in the first resurrection.
Some never see death or the resurrection but are alive and caught up to be with the Lord. (1 Thess 4:15-18)
All in Christ will reign with Him in the millennium.
Basically, this is all Revelation says about the thousand years.
The next Morning Thought deals with the post-millennial.