Metaphysics is the theoretical philosophy of being and knowing; philosophy of mind. At the lowest level of popular thinking, it is basically just theorizing about a subject. It needs to be pointed out that all religion is metaphysical. Religion is about ideas of being, and of knowing God. It is a spiritual philosophy for this life, and of the one to come.
This means that metaphysics is the rightful domain of religion. It is NOT the rightful domain of science. Science is supposed to stick to facts about matter and laws of physics. But hang on - LAWS of physics? Who made those laws? Why, they were in existence and controlling the universe even before humans came into being! So how about religious laws of morality? Is it wrong to have laws about morality? And how come irreligious people are universally agreed that humans need laws about morality, if society is not to become anarchic?
Moral law is not exclusively the domain of religions. All humanity is agreed that, for instance, it is morally wrong to murder another human. Religion cannot be blamed for 'transposing' that particular law of morality into metaphysics. A law forbidding murder has nothing to do with religious metaphysics when irreligious people also have such a moral law. Yet when Jesus stated moral laws, that was based upon not only upon the metaphysical evidence of God's existence (He being God incarnate - God in the flesh) but upon the laws of God that deal with the corruption in human hearts and minds. That takes us right back into metaphysics.
Now take note: it is the strident efforts of the godless that are causing sea-changes in morality today, for the godless are philosophising about behaviour and norms, so as to try to persuade the public to adopt their ideas of morality. It is the irreligious who are trying to justify their morality by dreaming up a philosophy that accommodates it - metaphysics, in other words. So please throw your question back at the godless who are presenting society with their fluid, and metaphysical ideas about morality. Jesus stuck to the ancient morality of the God who calls His people to be holy, no matter what society around them thinks about that.