How can I compare and contrast Sonnet 18 and Sonnet 130? How are they similar or different when talking about the theme of appearance?

In William Shakespeare’s Sonnet 18 and Sonnet 130, the speakers praise the beauty of their lovers through abundant metaphors and figurative imagery that uphold the theme of appearance. In Sonnet 18, the speaker begins his admiration with the initial lines of "Shall I compare thee to a summer’s day?  / Thou art more lovely and more temperate" (1-2).  Here, the speaker claims his love is more beautiful than a summer day, claiming “Rough winds do shake the darling buds of May, / And summer’s lease hath all too short a date” (3-4).  The beauty of his love is greater than a summer day because the fair season often has strong winds that damage delicate flowers and the season is fleeting—it never lasts.  Thus, the theme of appearance in Sonnet 18 is centered on the premise of youthful beauty, and the speaker goes to great lengths to compare his love to “nature’s changing course” (8).  However, in contrasting Sonnet 18 with Sonnet 130, the speaker never actually describes the physical appearance of his lover, but instead compares it to natural events, asserting the beauty is eternal.  The speaker states, “But thy eternal summer shall not fade, / Nor lose possession of that fair thou ow’st” (9-10).  Therefore, the theme of appearance is not grounded in the physical sense, but in the metaphysical sense that his lover’s beauty will be immortalized.  

Similar to Sonnet 18, Sonnet 130 compares a lover’s beauty to nature. The speaker begins with the following lines:

My mistress’ eyes are nothing like the sun;

Coral is far more red than her lips’ red;

If snow be white, why then her breasts are dun;

If hairs be wires, black wires grow on her head. (1-4)

Again, the first line compares the lover’s appearance to the sun, but does so in an adverse way. The speaker again notes how his lover’s beauty is incomparable to natural elements, such as “sun,” “coral,” “snow,” and “wires,” but in contrast to Sonnet 18, Sonnet 130 provides a physical description of the lover’s appearance.  Further, Sonnet 130 is more concerned with the physicality of the subject as opposed to the youthful soul and immortal beauty of the subject in Sonnet 18.  Thus, in terms of appearance, Sonnet 18 is metaphysical, while Sonnet 130 is physical.  The speaker of Sonnet 130 goes on to chastise other poets for exaggerating descriptions and using elaborate figurative language to describe their lovers.  The speaker concludes Sonnet 130 with the quatrain, “And yet, by heaven, I think my love as rare / As any she belied with false compare” (13-14). Here, the speaker pokes fun at poems that ridiculously compare women to beautiful nature, as those descriptions are often over-idolized and false representations. This line is ironic in terms of the language of Sonnet 18, but it simultaneously shows two stances on presenting a theme of appearance through poetic language.