Here "feet" represents Christ's lordship, authority, and power. Alternate translation: "all things under Christ's power" (See: [[rc://en/ta/man/translate/figs-metonymy]])
Just as with a human body, the head rules all things pertaining to its body, so Christ is the head of the church body. (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "head" refers to the leader or the one who is in charge. Alternate translation: "ruler over all things" (See: [[rc://en/ta/man/translate/figs-metaphor]])