Answer:
I fly when I'm on and float coming off.
What gets sharper the more you use it?
A move made popular by the King of Pop.
I am long and slim works in light. Has but one eye and an awful bite.
I cut through evil like a double edged sword and chaos flees at my approach. Balance I single-handedly upraise through battles fought with heart and mind instead of with my gaze.
No matter how little or how much you use me, you change me every month.