Shakespeare's sonnet 18 adheres to the sonnet form, 3 stanzas of 4 lines and a finishing couplet, ten syllables per line written in iambic pentameter. Robert Burns's poem is written in 4 stanzas of 4 lines each, alternating 8 and 6 syllable lines, written in iambic tetrameter and iambic trimeter respectively.

As far as the themes these poems convey, one poem could have inspired the other. They both speak of the permanence of love, of loving beyond all constraints of time.  Here the "summer day" and "red rose" of both poems express the transient nature of physical beauty, but the narrator in both conveys that their passion will not diminsh over time.