The Catechism in Questions & Answers

559. What will happen at the return of Christ?

In summary, the following results from the statements of Apostle Paul:
At the return of Christ, the dead who have died in Christ, will be the first to resurrect incorruptible. The living who have allowed themselves to be prepared for the return of Christ will experience the transformation without having to suffer physical death.
Both the dead and the living will receive a glorious body. This body will be like the resurrection body of Christ. Together, they will be caught up to Jesus Christ and will thus enter into eternal fellowship with the triune God.
These events are part of the first resurrection mentioned in Revelation 20: 5-6.

Resurrection: see Questions 574. et seq. Resurrection body: see Question 189.

‘Incorruptible’ means immortal, unperishable. Unlike our present body, the resurrection body will not be subject to decay.