To be changed means that believers will experience a transformation from corruptible bodies to incorruptible, spiritual bodies suitable for heaven.
The phrase 'we shall be changed' reflects a profound transformation that believers will undergo at Christ's return. In 1 Corinthians 15:51-52, Paul reveals that this change will occur in a moment, at the last trumpet, when our mortal bodies will put on immortality. This signifies that our current, sin-tainted bodies cannot inherit the kingdom of God, and instead, we will be given new, glorified bodies that are imperishable and suited for eternal communion with God. This promise provides hope and assurance that physical death is not the end, but rather the beginning of a glorious existence in the presence of Christ.
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