metre vs metrical foot

metre and metrical foot both are nouns.

Word	Noun	Adjective	Verb	Adverb
metre	Yes	No	No	No
metrical foot	Yes	No	No	No

As nouns, metrical foot is a hyponym of metre; that is, metrical foot is a word with a more specific, narrower meaning than metre:

metre: (prosody) the accent in a metrical foot of verse
metrical foot: (prosody) a group of 2 or 3 syllables forming the basic unit of poetic rhythm

Other hyponyms of metre include catalexis, scansion, common measure, common meter, foot, metrical unit.

metre (noun)	metrical foot (noun)
rhythm as given by division into parts of equal duration	(prosody) a group of 2 or 3 syllables forming the basic unit of poetic rhythm
(prosody) the accent in a metrical foot of verse
the basic unit of length adopted under the Systeme International d'Unites (approximately 1.094 yards)