metropolis vs Saigon

metropolis and Saigon both are nouns.

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

metropolis (noun)	Saigon (noun)
people living in a large densely populated municipality	a city in South Vietnam; formerly (as Saigon) it was the capital of French Indochina
a large and densely populated urban area; may include several independent administrative districts