As a metaphysical concept, do you believe free will exists? Or are you deterministic?

I personally don't. I think the idea of free will is silly, especially with such evidence against it, such as epiphenomenalism, psychology, learning patterns, reflexes, evolution, ingrained ideas, predispositions, mental disorders, fMRIs, etc. I think it's baffling that anyone can still believe in free will, at least without some overarching religion telling them "because I said so." Which, while I think is dumb, I can understand why someone would believe it.

Free will as an unpredictable physical occurrence, as Hawking defines it, obviously can exist. That is mathematically provable. Obviously the concepts exist, as we experience them; the issue is merely that they aren't what we think they are. Free will is an illusion, not a metaphysical operator.