Apocalyptic language communicated divine judgment, kingship, and the final vindication of God's people. Jesus' hearers would recognize the cloud-coming Son of Man as an allusion to Daniel 7.
Cloud imagery is especially significant in Scripture because clouds repeatedly accompany manifestations of God's presence and glory.
Daniel 7:13-14 portrays one like a son of man coming with the clouds of heaven and receiving dominion, glory, and a kingdom from the Ancient of Days. His rule is universal and everlasting.
Elsewhere in the Old Testament, riding or coming upon clouds is characteristic divine imagery, though Daniel's Son of Man remains distinguishable from the Ancient of Days.
Jesus predicts that the sign of the Son of Man will appear and that all peoples will see him coming on the clouds with power and great glory.
He then says the Son of Man will send 'his angels' to gather 'his elect' from the whole earth. The scope is cosmic and eschatological rather than merely national.
Daniel 7 provides the central framework: the Son of Man receives heavenly authority and universal dominion. Jesus identifies his own future with that figure.
The passage contributes strongly to divine-identity Christology through heavenly glory, cloud imagery, authority over angels, and the gathering of God's elect, while preserving the personal distinction between the Son of Man and the one from whom authority is received.