Hath made thee ruler over them all, i.e. hath given thee absolute dominion of all creatures, men and beasts, within the bounds of thy vast kingdom, to hunt, catch, or kill far thy use and pleasure. God as Lord paramount allows thee, his vassal and tenant at will, all this. This was not universal over all the world, but only within his large territories, which yet were bounded. Thou art this head of gold.
1. Why head? Because he was first in order, as the head is before the other parts, and the vision began in him, and descended downwards to the other three monarchies.
2. Why head of gold? Because of the vast riches wherein it abounded, and which the Chaldeans most coveted, and scraped from the spoils and tributes of all countries, Isaiah 10:13,14 Jer 51:41,44. Also this is called the golden head, because it stood longest, five hundred years, and was fortunate and flourishing to the last.