Thou, O king, art a king of kings: for the God of heaven hath given thee a kingdom, power, and strength, and glory.

Jamieson-Fausset-Brown Bible Commentary

37. Thou . art a king of kings-The committal of power in fullest plenitude belongs to Nebuchadnezzar personally, as having made Babylon the mighty empire it was. In twenty-three years after him the empire was ended: with him its greatness is identified (Da 4:30), his successors having done nothing notable. Not that he actually ruled every part of the globe, but that God granted him illimitable dominion in whatever direction his ambition led him, Egypt, Nineveh, Arabia, Syria, Tyre, and its Phonician colonies (Jer 27:5-8). Compare as to Cyrus, Ezr 1:2.

Matthew Henry's Concise Commentary

2:31-45 This image represented the kingdoms of the earth, that should successively rule the nations, and influence the affairs of the Jewish church. 1. The head of gold signified the Chaldean empire, then in being. 2. The breast and arms of silver signified the empire of the Medes and Persians. 3. The belly and thighs of brass signified the Grecian empire, founded by Alexander. 4. The legs and feet of iron signified the Roman empire. The Roman empire branched into ten kingdoms, as the toes of these feet. Some were weak as clay, others strong as iron. Endeavours have often been used to unite them, for strengthening the empire, but in vain. The stone cut out without hands, represented the kingdom of our Lord Jesus Christ, which should be set up in the kingdoms of the world, upon the ruins of Satan's kingdom in them. This was the Stone which the builders refused, because it was not cut out by their hands, but it is become the head stone of the corner. Of the increase of Christ's government and peace there shall be no end. The Lord shall reign, not only to the end of time, but when time and days shall be no more. As far as events have gone, the fulfilling this prophetic vision has been most exact and undeniable; future ages shall witness this Stone destroying the image, and filling the whole earth.