What's a lie? That there will be a Rapture or that it will be before the Tribulation?
Looks like you've accepted some propaganda, so kindly tell us verse by verse what you read and what you understand in 1 Thess 4:13-18.
A snippet from John Pipers view/with scripture:
"Then he gives two arguments in verse 3 which he unfolds in verses 4–12. First, we know the day of the Lord hasn't come because the rebellion, or the apostasy, must come first. And second, the man of lawlessness has to be revealed before the day of the Lord arrives: "For that day will not come, unless the rebellion [or: apostasy] comes first, and the man of lawlessness is revealed" (verse 3).
Then in verses 4–9 Paul describes the coming of the man of lawlessness and in verses 9–12 he describes the climax of the great apostasy.
The Pre-Tribulational View of the Second Coming
One of the questions that I want to deal with tonight is where the rapture fits in here. There is a large wing of the evangelical church today that believes the second coming of Christ is going to happen in two stages. First, Christ will come for the church; they will rise to meet him in the air, return with him to heaven for a period of seven years, and then after the great tribulation is over, return to the earth in judgment. This view of the second coming is called the "pre-tribulational" view because it says that Christ comes for the church before the tribulation.
This view has been popularized by the notes in the Scofield Reference Bible and by many Bible schools and some seminaries. It was the basis of Hal Lindsay's Late Great Planet Earth, and has inspired songs and movies about the sudden disappearance of the Christians out of the world at the time of rapture.
One Argument for the Post-Tribulational View
Tonight I hope to take this issue up in more detail. But for now let me just show you one of several arguments from 2 Thessalonians why I cannot follow this interpretation, as much as I love and respect those who do. Why am I a post-tribulationist, that is, why do I look forward with great anticipation not to a sudden departure from the world for seven years but to a great gathering to meet the Lord in the air as he comes with his mighty angels in flaming fire to establish his earthly kingdom, giving rest to his people and judgment to his enemies?
What the Thessalonians Were Alarmed About
The saints at Thessalonica were shaken and alarmed thinking that the day of the Lord is at hand. Now for the pre-tribulationist the "Day of the Lord" is the second half of the second coming after the tribulation. It is described in verse 8: "And then the lawless one will be revealed, and the Lord Jesus will slay him with the breath of his mouth and destroy him by his appearing and his coming."
This is the day of the Lord—not the quiet rapture when the saints are snatched away, but the glorious and overwhelming attack from heaven against the man of lawlessness and all evil."