This image's head was of fine {q} gold, his breast and his arms of silver, his belly and his thighs of brass,

(q) By gold, silver, brass, and iron are meant the Chaldean, Persian, Macedonian, and Roman kingdoms, which would successively rule all the world until Christ (who is here called the stone) himself comes, and destroys the last. And this was to assure the Jews that their affliction would not end with the empire of the Chaldeans, but that they should patiently await the coming of the Messiah, who would be at the end of this fourth monarchy.

King James Translators' Notes

thighs: or, sides

Jamieson-Fausset-Brown Bible Commentary

32. On ancient coins states are often represented by human figures. The head and higher parts signify the earlier times; the lower, the later times. The metals become successively baser and baser, implying the growing degeneracy from worse to worse. Hesiod, two hundred years before Daniel, had compared the four ages to the four metals in the same order; the idea is sanctioned here by Holy Writ. It was perhaps one of those fragments of revelation among the heathen derived from the tradition as to the fall of man. The metals lessen in specific gravity, as they downwards; silver is not so heavy as gold, brass not so heavy as silver, and iron not so heavy as brass, the weight thus being arranged in the reverse of stability [Tregelles]. Nebuchadnezzar derived his authority from God, not from man, nor as responsible to man. But the Persian king was so far dependent on others that he could not deliver Daniel from the princes (Da 6:14, 15); contrast Da 5:18, 19, as to Nebuchadnezzar's power from God, "whom he would he slew, and whom he would he kept alive" (compare Ezr 7:14; Es 1:13-16). Græco-Macedonia betrays its deterioration in its divisions, not united as Babylon and Persia. Iron is stronger than brass, but inferior in other respects; so Rome hardy and strong to tread down the nations, but less kingly and showing its chief deterioration in its last state. Each successive kingdom incorporates its predecessor (compare Da 5:28). Power that in Nebuchadnezzar's hands was a God-derived (Da 2:37, 38) autocracy, in the Persian king's was a rule resting on his nobility of person and birth, the nobles being his equals in rank, but not in office; in Greece, an aristocracy not of birth, but individual influence, in Rome, lowest of all, dependent entirely on popular choice, the emperor being appointed by popular military election.

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.