それは君の役には立つまい。

that (indicating an item or person near the listener, the action of the listener, or something on their mind); it; that time; then; there (indicating a place near the listener); you

topic marker particle; indicates contrast with another option (stated or unstated); adds emphasis

you; buddy; pal; monarch; ruler; sovereign; (one's) master

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

use; service; role; post; position; scoring combination (e.g. in mahjong, card games, etc.); hand

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

to stand; to rise; to stand up; to find oneself (e.g. in a difficult position); to depart (on a plane, train, etc.)

probably isn't (doesn't, won't, etc.); don't (doesn't) intend to; intend not to; must not; (when used in an imperative sentence) don't