metropolis vs Rockford

metropolis and Rockford both are nouns.

Word	Noun	Adjective	Verb	Adverb
metropolis	Yes	No	No	No
Rockford	Yes	No	No	No

metropolis (noun)	Rockford (noun)
people living in a large densely populated municipality	a city in northern Illinois
a large and densely populated urban area; may include several independent administrative districts