Gateway to the West vs metropolis

Gateway to the West and metropolis both are nouns.

Word	Noun	Adjective	Verb	Adverb
Gateway to the West	Yes	No	No	No
metropolis	Yes	No	No	No

Gateway to the West (noun)	metropolis (noun)
the largest city in Missouri; a busy river port on the Mississippi River near its confluence with the Missouri River; was an important staging area for wagon trains westward in the 19th century	people living in a large densely populated municipality
	a large and densely populated urban area; may include several independent administrative districts