metropolis vs concrete jungle

metropolis and concrete jungle both are nouns.

Word	Noun	Adjective	Verb	Adverb
metropolis	Yes	No	No	No
concrete jungle	Yes	No	No	No

metropolis (noun)	concrete jungle (noun)
people living in a large densely populated municipality	an area in a city with large modern buildings that is perceived as dangerous and unpleasant
a large and densely populated urban area; may include several independent administrative districts