Vatican City vs metropolis

Vatican City and metropolis both are nouns.

Word	Noun	Adjective	Verb	Adverb
Vatican City	Yes	No	No	No
metropolis	Yes	No	No	No

Vatican City (noun)	metropolis (noun)
the capital of the State of the Vatican City	people living in a large densely populated municipality
	a large and densely populated urban area; may include several independent administrative districts