metropolis vs Green Bay

metropolis and Green Bay both are nouns.

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

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