The coming of the Son of Man is the theme of the last part of Matthew 24 and also the first part of Matthew 25. The day and hour of His coming were unknown, but here it is. The Son of Man comes in His glory, to establish His Kingdom worldwide. He will sit on the throne in Jerusalem, for that is the city of the great King (Matt. 5:35) and the capital of the Messianic kingdom. Before Him the nations will be gathered (:32).
gone up to the land
Earlier we have seen that the Lord will first gather His people outside the land, in the desert, in Bozrah. From Bozrah, as King at the head of His people, He will go up to the land and take possession of it (Micah 2:12-13). When exactly this will take place, I have not (yet) been able to discover in Scripture.
sixth bowl and sixth trumpet
We do know that the Lord is present in the land at the time of the sixth bowl, which we find described in Revelation and which runs parallel to the sixth trumpet. The nations rebel against YAHWEH and His Anointed at the sixth bowl (Ps. 2:2) and are gathered at Armageddon (Rev. 16:16), in the valley of Megiddo, also called the plain of Jezreel. There these armies of the nations will be destroyed, He will crush them (Ps. 2:9).
31 And when the Son of Man comes in His glory, and all the holy messengers with Him, then He will sit on the throne of His glory.
all the holy messengers with Him
The Lord does not come alone, we read. It says that He comes, and all the holy messengers with Him. Here it concerns His coming for the nations (:32).
Earlier we saw that in Matthew 24:30 His coming for Israel is spoken of. At the end of the great tribulation (Matt. 24:29) His feet will stand on the Mount of Olives (Zech. 14:4) and He will appear to the Jewish people. Here too the Lord does not appear alone. In Zechariah it is stated that He comes: and all the saints with Him (Zech. 14:5). In the description of His appearance to Israel in Matthew 24, we saw that He comes on the clouds with great power and glory (Matt. 24:30).
with Him revealed in glory
These additions in Zechariah 14:5, Matthew 24:30 and Matthew 25:31 are very similar and all refer to the same thing: the company with which the Lord appears.
Before the great tribulation, the ecclesia is caught away and united with the Lord. Paul says about this: and so we shall always be together with the Lord (1 Thess. 4:17). When He then appears later, that is Christ the Head, with the ecclesia, His body. Both Matthew 24:30 and Matthew 25:31 speak of His appearing in glory and we will be there.
Colossians 3
4 When Christ, who is our life, is revealed, then you also will be revealed with Him in glory.
the 144,000?
The word messengers (Greek: aggelos) appears four times in these chapters. In Matthew 24:36 it concerns the messengers of the heavens, who are angels. In Matthew 25:41 it concerns the devil and his messengers.
In Matthew 24:31, which we discussed earlier, the messengers are the 144,000, who proclaim the gospel of the kingdom and gather the elect (>Israel) from the four winds.
In Matthew 25:31 it is said that there are holy messengers, who will accompany Christ when He appears in glory. Therefore I think it concerns the ecclesia (Rom.1:7; 1 Cor.1:2; 2 Thess.1:7,10). But if the holy messengers here are the 144,000, then the Lord is accompanied by both the ecclesia, which is His body, and by the 144,000.