What happens to the Church in heaven after the Rapture?
After the rapture, the Church stands before the judgment seat of Christ at the sea of glass mingled with fire, where every believer's works are tested and rewarded, and their natural bodies are transformed into spiritual bodies before they return with Christ to reign in the Millennium.
Once the Church is caught up and arrives in Heaven, the first place the saints come to is a sea of glass mingled with fire. This is described as the very fire that will try the works each believer has done, such as the souls they helped bring into the Kingdom, the ministry that edified others, and the lives that were touched through their obedience. Only those whose labor has borne fruit will stand at this judgment; those without fruit will not appear there because their destiny was already sealed while still on the earth.
Scripture teaches that every soul must appear before the judgment seat of Christ to receive for the things done in the body, whether good or bad, and that the Lord will reward every man according to his works. Paul's teaching in First Corinthians explains that whatever is built on the foundation of Christ, whether gold, silver, precious stones, or wood, hay, and stubble, will be tested by fire. If the work abides, the believer receives a reward; if it is burned, the believer suffers loss but is still saved, yet as by fire so that no one who truly belongs to Christ is in danger of losing their own soul.
Along with this judgment of works, the saints receive a new body. The natural body is transformed into a spiritual body at the rapture, described as a house not made with hands, eternal in the heavens, so that mortality is swallowed up by life. This resurrection body is raised in incorruption, in glory, and in power, in contrast to the corruption, dishonor, and weakness of the earthly body.
After these things, the saints are shown standing on the sea of glass with harps of God, worshiping the Lord and declaring that His judgments are made manifest. The kingdoms of this world then become the kingdoms of the Lord and of His Christ, and the reward is given to the prophets, the saints, and all who fear His name. From there, the Church returns with Christ to reign with Him when His kingdom is established on the earth in the Millennium.
The scriptures
For we must all appear before the judgment seat of Christ; that every one may receive the things done in his body, according to that he hath done, whether it be good or bad.
And, behold, I come quickly; and my reward is with me, to give every man according as his work shall be.
For the Son of man shall come in the glory of his Father with his angels; and then he shall reward every man according to his works.
And the seventh angel sounded; and there were great voices in heaven, saying, The kingdoms of this world are become the kingdoms of our Lord, and of his Christ; and he shall reign for ever and ever.
And the nations were angry, and thy wrath is come, and the time of the dead, that they should be judged, and that thou shouldest give reward unto thy servants the prophets, and to the saints, and them that fear thy name, small and great; and shouldest destroy them which destroy the earth.
And I saw as it were a sea of glass mingled with fire: and them that had gotten the victory over the beast, and over his image, and over his mark, and over the number of his name, stand on the sea of glass, having the harps of God. And they sing the song of Moses the servant of God, and the song of the Lamb, saying, Great and marvellous are thy works, Lord God Almighty; just and true are thy ways, thou King of saints. Who shall not fear thee, O Lord, and glorify thy name? for thou only art holy: for all nations shall come and worship before thee; for thy judgments are made manifest.
I have planted, Apollos watered; but God gave the increase. So then neither is he that planteth any thing, neither he that watereth; but God that giveth the increase. Now he that planteth and he that watereth are one: and every man shall receive his own reward according to his own labour. For we are labourers together with God: ye are God’s husbandry, ye are God’s building. According to the grace of God which is given unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. But let every man take heed how he buildeth thereupon. For other foundation can no man lay than that is laid, which is Jesus Christ. Now if any man build upon this foundation gold, silver, precious stones, wood, hay, stubble; Every man’s work shall be made manifest: for the day shall declare it, because it shall be revealed by fire; and the fire shall try every man’s work of what sort it is. If any man’s work abide which he hath built thereupon, he shall receive a reward. If any man’s work shall be burned, he shall suffer loss: but he himself shall be saved; yet so as by fire.
For we know that if our earthly house of this tabernacle were dissolved, we have a building of God, an house not made with hands, eternal in the heavens. For in this we groan, earnestly desiring to be clothed upon with our house which is from heaven: If so be that being clothed we shall not be found naked. For we that are in this tabernacle do groan, being burdened: not for that we would be unclothed, but clothed upon, that mortality might be swallowed up of life.
From the books
This answer is drawn from these passages in the Mary Banks Faith Library.