But we do not want you to be uninformed, brothers and sisters, about those who have died, so that you may not grieve as others do who have no hope. For since we believe that Jesus died and rose again, even so, through Jesus, God will bring with him those who have died. For this we declare to you by the word of the Lord, that we who are alive, who are left until the coming of the Lord, will by no means precede those who have died. For the Lord himself, with a cry of command, with the archangel’s call and with the sound of God’s trumpet, will descend from heaven, and the dead in Christ will rise first. Then we who are alive, who are left, will be caught up in the clouds together with them to meet the Lord in the air; and so we will be with the Lord forever. Therefore encourage one another with these words. (1 Thessalonians 4:13-18, NRSV)
This is the basis of the rapture.
We will be lifted up into the sky and some will be left behind…
But if you read this carefully you see that those left behind are the ones who have not yet died. So if you are reading this according to this reading you are one who is left behind.
It is not about a time when some will be taken and others will be left to go through a tribulation period.
This verse is about the hope we have in Jesus Christ to fulfill the promise, that we will be with him forever.