Aachen vs metropolis

Aachen and metropolis both are nouns.

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

Aachen (noun)	metropolis (noun)
a city in western Germany near the Dutch and Belgian borders; formerly it was Charlemagne's northern capital	people living in a large densely populated municipality
	a large and densely populated urban area; may include several independent administrative districts