Shakespeare's Sonnet 116 uses the following traditional rhyme scheme:
a b a b c d c d e f e f gg
with the quatrains (four-line stanzas) each using self-contained rhymes (the rhymes are not shared) and the closing couplet (pair of rhymed lines) set apart. The self-contained rhymes reflect and contribute to the content, in the sense that each quatrain uses its own line of thought just as it contains its own rhymes. Rhyme, as always, creates unity, as well.
Metaphor is the dominant figure of speech in the poem. We read: love doesn't bend with the remover, love is a mark (an unspecified nautical device), love is a star, love is not time's fool (court jester), the grim reaper's sickle swipes like the arc of a compass. The metaphors create a series of images used to describe love.
The poem closes with a paradox--if what the speaker says is not true, then he has never written, and no man has ever loved.