City of Brotherly Love vs metropolis

City of Brotherly Love and metropolis both are nouns.

Word	Noun	Adjective	Verb	Adverb
City of Brotherly Love	Yes	No	No	No
metropolis	Yes	No	No	No

City of Brotherly Love (noun)	metropolis (noun)
the largest city in Pennsylvania; located in the southeastern part of the state on the Delaware river; site of Independence Hall where the Declaration of Independence and the Constitution were signed; site of the University of Pennsylvania	people living in a large densely populated municipality
	a large and densely populated urban area; may include several independent administrative districts