metal drum vs vessel

metal drum and vessel both are nouns.

Word	Noun	Adjective	Verb	Adverb
metal drum	Yes	No	No	No
vessel	Yes	No	No	No

As nouns, vessel is a hypernym of metal drum; that is, vessel is a word with a broader meaning than metal drum:

metal drum: a cylindrical metal container, commonly used for shipping or storage of liquids
vessel: an object used as a container (especially for liquids)

metal drum (noun)	vessel (noun)
a cylindrical metal container, commonly used for shipping or storage of liquids	a craft designed for water transportation
	an object used as a container (especially for liquids)
	a tube in which a body fluid circulates