Saigon vs metropolis

Saigon and metropolis both are nouns.

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

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