Shakespeare relies on strong visual imagery to deliver the similes in Sonnet 130. These devices ultimately demonstrate the type of love he shares with his beloved.

For the majority of this sonnet, the reader is left a bit perplexed. After all, this woman doesn't seem to really captivate the speaker's interests. Her lips are so pale that even coral has more color. Her breasts are not the color of a winter snow but instead are "dun," which is a gray-brown color. Her hair is not soft and lustrous; instead, it resembles black wires sticking out of her head. This woman's cheeks lack the rosiness associated with youth and vitality. The speaker even insults the woman's breath, noting that it "reeks," and points out that her voice is not particularly melodic.

After this list of visual, auditory, and olfactory imagery, a sense of confusion settles in upon the reader. What, exactly, does attract the speaker to his "mistress"? Finally, in the ending couplet, the speaker acknowledges that despite this woman's appearance, his love for her is rare and far more valuable than those whose relationships are based on falsehoods.

Ultimately, then, this poem is also a satire. By its use of imagery and similes, it gently makes fun of typical romantic poetry. Such poetry often uses over-the-top imagery which nearly creates saints out of its subjects. The speaker is thus able to make his ultimate point that he recognizes the shortcomings of his mistress, unlike other poets, and loves her for exactly who she is.

In "Sonnet 130," Shakespeare employs antithesis throughout the poem to emphasize the difference between his mistress and the idealized subjects of more conventional sonnets. This antithesis is achieved by reversing the familiar figure of the simile, as he makes comparisons by stressing the differences between two objects.

The first such reverse simile states that his mistress's eyes "are nothing like the sun." The comparison of a woman's eyes to the sun and stars is thoroughly conventional (it occurs in Romeo and Juliet and many other works of romantic literature), but a moment's thought shows that this is not a point about his mistress at all, but about the ludicrous nature of such comparisons. Nobody's eyes look like the sun, and the effect would be terrifying if they did.

The reverse similes, which also function as visual imagery, continue throughout the poem. Coral is redder than her lips, and snow is whiter that her breasts. Her cheeks look unlike roses, her breath smells unlike perfume, her voice sounds unlike music, and she walks unlike a goddess. Amongst these, there is one metaphor: "black wires grow on her head."

By reversing the similes in "Sonnet 130," Shakespeare also points out and reverses the hyperbole, which is a feature of love poetry. If it is both a simile and an instance of hyperbole to say that your mistress's eyes are like the sun, then to say that they are nothing like the sun reverses and subverts both.

Shakespeare employs a negative simile when the narrator says that his "mistress' eyes are nothing like the sun."  In other words, he will not flatter her by comparing her beauty to objects to which it cannot possible measure up, unlike most typical love sonnets which make such lofty, untruthful comparisons.  Shakespeare employs a metaphor when the narrator says, "If hairs be wires, black wires grow on her head."  He compares her hair to wires, rather than flatter her by comparing it to something more luxurious and less plausible.  He does employ visual imagery when he describes the "roses damasked, red and white," though he cannot claim to see roses in his lover's cheeks.  The narrator considers comparing his lover's voice to music and her walk to a goddess' tread, but he stops short of actually using a figure of speech to do so because she really cannot compare in either case.  His point is that he does not need to make false comparisons, as others do, because he knows how special his love is already.  He doesn't love her in spite of her defects precisely because he does not see that she has defects.  She is a human, and he describes her as one.

Here is the sonnet:

SONNET 130

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.
I have seen roses damask'd, red and white,
But no such roses see I in her cheeks;
And in some perfumes is there more delight
Than in the breath that from my mistress reeks.
I love to hear her speak, yet well I know
That music hath a far more pleasing sound;
I grant I never saw a goddess go;
My mistress, when she walks, treads on the ground:
   And yet, by heaven, I think my love as rare
   As any she belied with false compare

This sonnet is a parody of the traditional Elizabethan love sonnet. It seems like the author is criticizing his love more than praising her. He lists the many things that do NOT describe his love. Many of these things are used in traditional sonnets to describe one's love - voice like music, cheeks like roses, golden hair, etc. This man's love, however, is none of these things, and yet he loves her anyway. He does not need to compare her to false things.

Here are some poetic devices. Lots of similes and metaphors:

1. Simile - eyes are nothing like the sun (this is a negative simile, he says her eyes are not like the sun).

2. Metaphor - comparing her lips to coral (another negative - he says her lips are not red like coral)

3. Metaphor - comparing her voice to music (it is NOT like music)

Now, see if you can give it a try. What other comparisons does he make? Remember, they are mostly negative comparisons!

Read about Shakespeare's sonnets here on enotes.