The poem’s rhyme scheme is ABA / ABC / BCB. Its nine lines are in iambic tetrameter and iambic dimeter. Iambic tetrameter is a line composed of four iambs or beats (syllables), and iambic dimeter is a line composed of two iambs. The rhyme scheme is used to support the ideas of fire and ice, since different alphabet sounds carry different ideas that are expressed in the poem. The speaker presents two opposing viewpoints in the poem and discusses two possibilities regarding the world’s end. The rhyme scheme and repetition of the words “fire,” “desire,” “ice,” and “twice” act as unifiers in the poem. The rhyme also works with the repetition of the words “fire” (Line 1, Line 3) and “ice” (Line 2, Line 7) to create motion in the poem. This motion mimics the waves and undulations of burning flames and the molecular changes involved in freezing. The motion created by the rhyme and repetitions also conveys the speaker’s decision-making process.