It is true that ethics and metaphysics are distinct inquiries. Metaphysics is concerned with the most pervasive features of reality or the fundamental nature of reality. Ethics by contrast is occupied with concepts such as good, bad, the right, the obligatory, the permissible, the just, both to analyse and inter-relate them and (in meta-ethics) to examine the truth-status of ethical claims and of bodies of ethical theory that are prescriptive and tell us what we should or should not do - theories such as Kantianism and utiltiarianism. Not only whether they are true but whether they are capable of truth and not rather (say) expressions of emotion or attitude or mere social convention.
Though distinct, however, ethics and metaphysics are related. The reason is that you cannot do ethics without making assumptions about the nature of reality. Do we have free will ? This is a metaphysical question; ethics cannot answer it. Is there an independently existing moral reality by virtue of which (say by correspondence or some other theory of truth) ethical claims - moral judgements - can be true or false ? This question again falls outside ethics and belongs to metaphysics.
Oldest of all, does morality depend in some sense on the existence of God ? If you think that morality is a matter of divine command, then you assume the existence of a God with certain attributes. The existence of God is no question for ethics but falls within metaphysics.
The brief answer to your question is that ethics and metaphysics are distinct - they are not the same subject - but that moral judgements and ethical thoeries of all sorts contain metaphysical presuppositions.