gravity

I'm not happy with the notion that something could "be" metaphysical instead of natural. We can propose metaphysical explanations for phenomena that don't have a physical explanation (yet), such as lightning, but it's only the explanation that is either physical or metaphysical. The phenomenon itself just "is".

You seem to be using "metaphysical" as a synonym for "supernatural", which I don't think is correct.

Of course the problem with "supernatural" explanations is that they're so often made redundant by natural explanations - e.g. lightning. I think we should regard "supernatural" as something like "ultraviolet" - i.e. "beyond visible light, "more" than visible light in the sense that it's more energetic, but not fundamentally different from visible light.