en_tn/1th/04/16.md

the Lord himself will descend

"the Lord himself will come down"

the archangel

"the chief angel"

the dead in Christ will rise first

The "dead in Christ" are those believers who have passed away. AT: "those who believe in Jesus Christ, but who have already died, will rise first" (See: rc://en/ta/man/translate/figs-explicit)