Psa 110:4 The LORD has sworn and will not repent, Thou art a priest for ever after the order of Melchizedek.
Psa 110:5 The Lord at thy right hand shall smite the kings in the day of his wrath.
Psa 110:6 He shall judge among the Gentiles; he shall fill their places with dead bodies; he shall wound the head over much of the earth
the meaning of killing kings and judging gentiles , i think is understood properly
in terms of that gentiles are symbolic of the unconscious subconscious sins in believers
lacking a fully renewed mind
thus when believers are ready..Psa 110:3 Thy people shall be willing in the day of thy power
..the exposing and purging of their remaining indwelling sins can be accomplished
and the believer attains a renewed matured mind able to fully discern the word..."; therefore he shall lift up his head. "