Yes, I think the term refers to that which is beyond
this experienced world; it would in that case refer to Kant's noumenal realm and even the Christian's other-worldly "heaven." I prefer Nietzsche's this-worldly attitude--all that really matters is what we experience in this
life. On the other hand some would consider his Eternal Recurrence to be metaphysical, but that's only if you take his cyclical model of existence literally; I don't. On still another hand, some might consider the metaphsical to refer to that which is fundamental, to our most basic presuppositions. In that case, Nietzsche's Will to Power might qualify as a metaphysical notion because it refers virtually to a quality of everything.