Who is "Son Of Man" in Bible that Bible (Matthew 24:30) says that He Will return with Jesus ??

Son of man. An expression found about 80 times in the Gospels. It applies to Jesus Christ and shows that by means of his fleshly birth, he became a human and was not simply a spirit creature with a materialized body. The phrase also indicates that Jesus would fulfill the prophecy recorded at Daniel 7:13, 14. In the Hebrew Scriptures, this expression was used for Ezekiel and Daniel, highlighting the difference between these mortal spokesmen and the divine Originator of their message.—Eze 3:17; Da 8:17; Mt 19:28; 20:28.

Jesus’ application of this expression to himself clearly showed that God’s Son was now indeed a human, having ‘become flesh’ (John 1:14), having ‘come to be out of a woman’ through his conception and birth to the Jewish virgin Mary. (Galations 4:4; Lu 1:34-36) Hence he had not simply materialized a human body as angels had previously done; he was not an incarnation but was actually a ‘son of mankind’ through his human mother.

The designation “Son of man,” therefore, also serves to identify Jesus Christ as the great Kinsman of mankind, having the power to redeem them from bondage to sin and death, as well as to identify him as the great Avenger of blood.—Le 25:48, 49; Nu 35:1-29.

At some point after the “great tribulation” begins, but before Jehovah executes his judgment upon the rest of this world, supernatural events will occur. Note the effect they will have. “Then the sign of the Son of man [Christ] will appear in heaven, and then all the tribes of the earth will beat themselves in lamentation, and they will see the Son of man coming on the clouds of heaven with power and great glory.” (Matthew 24:29, 30) “There will be signs in sun and moon and stars, . . . while men become faint out of fear and expectation of the things coming upon the inhabited earth.”—Luke 21:25, 26.