Who Will Be Caught Up?

The passage above is describing the parousia, the same Greek term used in Matthew, Chapter 24. It is not a "secret coming," it is the appearing of Christ in the historic Day of the Lord.
The doctrine of the "rapture" is based on I Thessalonians 4:17. The rapture doctrine is harmful. The Bible admonishes us to prepare ourselves to stand in the evil day. The rapture doctrine tells us there will be no evil day. As a result, God's people are unprepared for the moral and physical chaos of the closing days of the Church Age.
Therefore put on the full armor of God, so that when the day of evil comes, you may be able to stand your ground, and after you have done everything, to stand. (Ephesians 6:13)
There indeed is coming a "day of evil." The rain of Divine judgment is going to fall on the world. The only safety will be in the Ark, Christ. So we need to press into Him fervently without delay.
I am certain that Noah and his three sons, and his wife and their wives if they helped, did not build this massive vessel in a week or two. In like manner, as we are learning to press into Christ, our entrance into the "ark" will be occurring throughout our lifetime.
When you think back about Noah, Daniel, Peter in jail, the three Hebrew young men in the time of Nebuchadnezzar, we can see that God can deliver us in the most unlikely circumstances. However, as in the case of the Christians in the Arena in Rome, we may be delivered from danger by dying.
In no instance that I can think of did God deliver people from trouble by lifting them bodily to Heaven to escape problems on the earth.
But we are not going to prepare ourselves to stand our ground if we believe we will be taken out of the world before the days are evil, before it "rains," we might say.