metropolis vs Sioux City

metropolis and Sioux City both are nouns.

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

metropolis (noun)	Sioux City (noun)
people living in a large densely populated municipality	a city in northeastern Iowa where the Big Sioux River joins the Missouri
a large and densely populated urban area; may include several independent administrative districts