The second coming of Christ is a fundamental doctrine in the scriptures.
Christ is the promised king who will sit on David’s throne.
Luke 1:32 He shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him the throne of his father David: 33 And he shall reign over the house of Jacob for ever; and of his kingdom there shall be no end.
He is to be king over all the earth.
Psalms 2:7 I will declare the decree: the LORD hath said unto me, Thou art my Son; this day have I begotten thee. 8 Ask of me, and I shall give thee the heathen for thine inheritance, and the uttermost parts of the earth for thy possession. 9 Thou shalt break them with a rod of iron; thou shalt dash them in pieces like a potter’s vessel.
His stay in heaven is temporary.
Acts 1:6 When they therefore were come together, they asked of him, saying, Lord, wilt thou at this time restore again the kingdom to Israel? 7 And he said unto them, It is not for you to know the times or the seasons, which the Father hath put in his own power. 8 But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth. 9 And when he had spoken these things, while they beheld, he was taken up; and a cloud received him out of their sight. 10 And while they looked stedfastly toward heaven as he went up, behold, two men stood by them in white apparel; 11 Which also said, Ye men of Galilee, why stand ye gazing up into heaven? this same Jesus, which is taken up from you into heaven, shall so come in like manner as ye have seen him go into heaven.
Acts 3:21 Whom the heaven must receive until the times of restitution of all things, which God hath spoken by the mouth of all his holy prophets since the world began.
He has been appointed judge.
Acts 17:31 Because he (God) hath appointed a day, in the which he will judge the world in righteousness by that man whom he hath ordained; whereof he hath given assurance unto all men, in that he hath raised him from the dead.
At his return, he will raise and judge the dead.
John 5:28 Marvel not at this: for the hour is coming, in the which all that are in the graves shall hear his voice, 29 And shall come forth; they that have done good, unto the resurrection of life; and they that have done evil, unto the resurrection of damnation.
The faithful will rule with him over the earth for 1000 years.
Revelation 20:6 Blessed and holy is he that hath part in the first resurrection: on such the second death hath no power, but they shall be priests of God and of Christ, and shall reign with him a thousand years.
At the end of the millennial reign there will be a second resurrection and a final judgment.
Revelation 20:13 And the sea gave up the dead which were in it; and death and hell (hades – the grave) delivered up the dead which were in them: and they were judged every man according to their works.
Sin and death will be eradicated and all who live on will possess the divine nature.
2 Peter 1:4 Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust.
This will be the fulfilment of God’s purpose which is to fill the earth with his glory in the form of men and women made equal to the angels with whom and in whom God will dwell forever.
Numbers 14:21 But as truly as I live, all the earth shall be filled with the glory of the LORD.
Paul explains what is going to happen:
1 Corinthians 15:20 But now is Christ risen from the dead, and become the firstfruits of them that slept. 21 For since by man came death, by man came also the resurrection of the dead. 22 For as in Adam all die, even so in Christ shall all be made alive. 23 But every man in his own order: Christ the firstfruits; afterward they that are Christ’s at his coming. 24 Then cometh the end, when he shall have delivered up the kingdom to God, even the Father; when he shall have put down all rule and all authority and power. 25 For he must reign (the millennial reign), till he hath put all enemies under his feet. 26 The last enemy that shall be destroyed is death. 27 For he hath put all things under his feet. But when he saith all things are put under him, it is manifest that he is excepted, which did put all things under him. 28 And when all things shall be subdued unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all.
Revelation describes this time.
Revelation 21:3 And I heard a great voice out of heaven saying, Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, and be their God. 4 And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away.
I hope you find this helpful.