ontology vs metaphysics

ontology and metaphysics both are nouns.

Word	Noun	Adjective	Verb	Adverb
ontology	Yes	No	No	No
metaphysics	Yes	No	No	No

As nouns, metaphysics is a hypernym of ontology; that is, metaphysics is a word with a broader meaning than ontology:

ontology (noun)	metaphysics (noun)
the metaphysical study of the nature of being and existence	the philosophical study of being and knowing
(computer science) a rigorous and exhaustive organization of some knowledge domain that is usually hierarchical and contains all the relevant entities and their relations