New York City vs metropolis

New York City and metropolis both are nouns.

Word	Noun	Adjective	Verb	Adverb
New York City	Yes	No	No	No
metropolis	Yes	No	No	No

New York City (noun)	metropolis (noun)
the largest city in New York State and in the United States; located in southeastern New York at the mouth of the Hudson river; a major financial and cultural center	people living in a large densely populated municipality
	a large and densely populated urban area; may include several independent administrative districts