Jermaine asked: What is the sign of the Son of Man that will be seen in Heaven according to Matthew 24:30?
Well, Jermaine, we're not entirely sure, but I'll tell you what we can know.
What Matthew is describing is Jesus' return to earth at the end of the Great Tribulation. Jesus told His disciples in that passage that at the end of this time of tribulation, the entire world would see Him coming on the clouds.
We know that this is not Jesus coming to rapture the church. The whole world does not see the rapture of the church, but the whole world does see Jesus’ second coming. In the rapture, only the church will be taken up to meet Him in the clouds. We will then be taken to the Father’s house (John 14). In His second coming, Christ will come in the clouds, not for His people, but with His people, seen by all the world. He will set up His reign upon the earth.
As to the sign, there are two common ideas of what that might refer to.
One popular view is that it will be a light and/or a cloud. Think back to the time of the Exodus when God led His people with His Shekinah glory. A light and a cloud led Israel. Many believe that something like that will surround Jesus when He comes.
When Jesus ascended to Heaven in a cloud, an angel told His disciples that He would return the same way (Acts 1:11). The clouds symbolize the heavenly origin and character of the King.
A second view held by many people is that the sign will simply be Jesus Himself. When Christ appears, it will signify the imminent judgment that He brings.
While I hold to the first view, that light and clouds will surround Jesus, we don't know for sure.