“The Fly” consists of six stanzas of eight lines each, or octaves. Each octave follows similar rhyme and metrical structures. With minor variations, the poem’s octaves begin with five lines of iambic pentameter followed be one line of iambic tetrameter, one line of iambic trimeter, and a final line of iambic tetrameter. An iamb is a single metrical foot consisting of one unstressed syllable followed by one stressed syllable. The line “That Learns to kill to teach” (Line 23), for instance, is made up of three iambs. Pentameter, tetrameter, and trimeter refer to the lines having five, four, and three of such feet, respectively.

With the exception of the first octave, which follows an ABABCDDC rhyme scheme, every stanza rhymes ABCBDEED. In these later stanzas, the first and third lines tend to share a semantic field, such as “paws” (Line 17) and “hand” (Line 19) or “death” (Line 25) and “war” (Line 27). In this way, the ABABCDDC rhyme scheme of the first stanza continues semantically. Though the poem’s structure is fairly untraditional, its adherence to a relatively strict stanzaic structure and rhyme scheme distinguishes it from much of the contemporary experimental poetry.