The poem's opening phrase implies that the speaker's lover has just questioned their commitment. "Ask me no more," the speaker begins, "What I would suffer for my love." In other words: Stop asking me what terrible things I'd go through in the name of love!
The rest of the poem then consists of the speaker attempting to "prove" the "truth" of their love—to show their lover just how committed they really are.
These lines establish the poem's use of iambic tetrameter. This means that each line has four iambs, poetic units that follow an unstressed-stressed syllabic pattern (da-DUM), for a total of eight syllables per line. Iambic meters are very common in English language poetry because they approximate the sound of regular speech. Here, they also create a sense of rhythmic momentum and intensity.
Yet there's a variation on this meter from the poem's very first moment. "Ask me" scans most naturally as a trochee, a foot with a stressed-unstressed beat pattern, while the next foot is a spondee (two stressed beats in a row):
Ask me | no more, | my truth | to prove,
What I | would suf- | fer for | my love.
This begins things on a rousing, forceful note that conveys the force of the speaker's command to their listener. Note, too, the /m/ alliteration of "me," "more," and "my." This lends even more strength to the poem's opening, signaling the speaker's determination to make their case.
Finally, these two lines create a rhyming couplet: "prove" rhymes with "love" (though this sounds like a slant rhyme to modern ears, it wouldn't have been in Tollet's time). The poem will use couplets throughout, which makes sense: couplets are rhyming pairs, and the speaker is describing their devotion to a partnership. The consistent rhyme here and throughout the poem subtly reflects the strength of the bond between the speaker and the poem's addressee.