QUESTION: What "transformation" will the Lord Jesus effect in the bodies of believers alive on earth at the end of the Tribulation to fit them to live in the Millennium?
RESPONSE: None. No believers will be left on earth after the Rapture. There will probably be millions who, never having rejected Christ, will believe during the Tribulation. Most of them will be martyred for their faith and will be resurrected at the Second Coming (Rv 20:4). They will have new bodies and will be part of the church. Both Jews and Gentiles who become believers during the Tribulation will continue on earth during the Millennium in their same earth bodies, so no transformation is needed. Yes, earth's inhabitants during that period will live much longer (Is 65:20), perhaps some the entire 1,000 years, but I think that will be a manifestation of God's grace and of the cleansed earth, not of super bodies.