The Italian Sonnet form of "Ozymandias" by Percy Bysshe Shelley imposes creative constraints on the poem, which helps the poet focus and formulate his message to his readers.
The poem is fourteen lines. It consists of an eight line section that develops the story, and a six line section that expounds on and analyzes the story. The rhyme of the poem adds to the success of the sonnet. This gives the poem a musical quality that helps one absorb and remember the lines. This contributes to easier consideration of the poem and a better understanding of it. The rhyme scheme of the first eight lines is ABAB ACDC. Rhymes include land, sand, command; stone, frown, and read, fed.
The six line section of the poem has the rhyme scheme EDE FEF. Rhymes include appear, despair, bear; things from the first eight lines rhyming with Kings in the six line section, and decay, away. Again the use of rhyme affects creative word choices, and done properly adds cohesion and a traceable line that adds formality to the poem and helps delineate its meaning.
Alliteration in the sonnet, such as "cold command", "survive, stamped", as well as "boundless and bare", add to the sound effects so-to-speak of this poem and this gives the sonnet an aural quality that makes the memorization and subsequent pondering of it conducive to a deeper understanding of the poem.
The iambic pentameter of the poem influences word choices and line lengths. This makes the poet very particular as to what words he includes in the poem; he does not want to haphazardly choose words of triteness that do not exactly convey the heart of the poem.