“Sonnet 18” may very well be Shakespeare’s best-known sonnet, beginning with the so-often quoted line: “Shall I compare thee to summer’s day?” Popular not only for its straight-forward discussion of love, beauty, and art, the poem is lauded for its accessibility and simplicity. Unlike many other sonnets in Shakespeare’s oeuvre, “Sonnet 18” is to the point, as it is unadorned by little more than the metaphorical comparison of the beloved’s beauty to that of a summer’s day.

The Shakespearean Sonnet, an unconventional sonnet structure that “Sonnet 18” by necessity conforms to, is composed of a single stanza of three quatrains and a couplet. Written in iambic pentameter and containing five sets of two stressed and unstressed syllables, the Shakespearean Sonnet always adheres to an ABAB CDCD EFEF GG rhyme scheme to differentiate between the quatrains. The final couplet is also known as a volta, a moment in which the poem turns, changing direction, perspective, or meaning at the very end. In “Sonnet 18,” the volta turns the discussion from the beauty of the speaker’s beloved to an acknowledgment of the power the poet wields, defying Death and rejecting life’s inalterable truth by recording and therefore preserving his lover’s indescribable appearance.

In the first line, the speaker speaks to an unknown subject; as he questions this subject that may or not be present, the speaker engages in apostrophe, speaking to an absent form.  He also introduces the metaphor that pervades the rest of the poem, comparing his beloved to a “summer’s day.” In the lines that follow, he focuses on several aspects of summer that make it volatile and unpredictable, using these undesirable examples to indicate that his beloved is not only more “lovely” but also more “temperate” and consistent. His appearance outstrips nature’s most winning state, a summer’s day, and does so without risking “the eye of heaven” becoming either “too hot” or “dimm’d.” As the sonnet progresses, the speaker dismisses summer’s virtues entirely, moving from the season’s physical form and using it as a metaphor for youthful vigor and appearance. He mourns the summer’s end, when fairness “declines,” and wishes for the youth to live on in “eternal summer.” This sense of immortal beauty is impossible and unattainable, yet the speaker imagines that his poetry might accomplish such a task. 

Even though the sonnet acts as a means of rendering the youth ageless and “eternal,” the speaker worries after the personified desires of Death, figured as a greedy character who might steal life’s glorious beauty and “brag” about owning it. This personification of life’s natural end creates a black-and-white dynamic that makes an enemy of time, combatting the inevitable forces that press in upon the unnatural, almost divine beauty of the youth. The results of this combat may appear fruitless, yet the speaker argues that his writing acts as a salve, healing the damage wrought by time and preserving his beauty in words and recollections.

Interestingly, the speaker does not describe his beloved specifically, and the reader has little sense of the beloved's physical appearance or his personality characteristics. The speaker only compares the beloved to a summer's day, complete with all of the descriptions of the sun and the absence of bad weather. Many scholars observe that the sonnet is more about the intensity of the speaker's love and less about the character of the beloved himself.