`Meta' in Greek means over, and -- since when you jump over something you find yourself behind it in space and after in time -- it is also understood as behind and after. The word `metaphysics' is said to originate from the mere fact that the corresponding part of Aristotle's work was positioned right after the part called `physics'. But it is not unlikely that the term won a ready acceptance as denoting the whole field of knowledge because it conveyed the purpose of metaphysics, which is to reach beyond the nature (`physics') as we perceive it, and to discover the `true nature' of things, their ultimate essence and the reason for being. This is somewhat, but not much, different from the way we understand `meta' in the 20-th century. A metatheory is a theory about another theory, which considered as an object of knowledge: how true it is, how it comes into being, how it is used, how it can be improved, etc. A metaphysician, in contrast, would understand his knowledge as a knowledge about the world, like that of a physicist (scientist, generally), and not as a knowledge about the scientific theories (which is the realm of epistemology).
If so, metaphysics should take as honorable a place in physics as metamathematics in mathematics. But this is very far from being the case. It would be more accurate to describe the situation as exactly opposite. Popularly (and primarily by the `working masses' of physicists), metaphysics is considered as something opposite to physics, and utterly useless for it (if not for any reasonable purpose). I will argue below that this attitude is a hangover from the long outdated forms of empiricism and positivism. I will argue that metaphysics is physics.
A detractor of metaphysics would say that its propositions are mostly unverifiable, if intelligible at all, so it is hardly possible to assign any meaning to them. Thales taught that everything is water. The Pythagoreans taught that everything is number. Hegel taught that everything is a manifestation of the Absolute Spirit. And for Schopenhauer the world is will and representation. All this has nothing to do with science.