Green Bay vs metropolis

Green Bay and metropolis both are nouns.

Word	Noun	Adjective	Verb	Adverb
Green Bay	Yes	No	No	No
metropolis	Yes	No	No	No

Green Bay (noun)	metropolis (noun)
a city of eastern Wisconsin on an arm of Lake Michigan	people living in a large densely populated municipality
	a large and densely populated urban area; may include several independent administrative districts