What is an explanation for both the literal and figurative meaning of "Sonnet 130" by William Shakespeare?

The literal meaning of Sonnet 130 is that the speaker loves his mistress even though she is not aesthetically perfect. The speaker catalogs a number of ways in which his mistress falls short physically: Her eyes do not shine like the sun does, her lips are not as red as coral, and her breasts, rather than being white, are grey. Her hair resembles black wires, and her cheeks are not red like roses. She has putrid breath, and her voice is not pleasing. 
The figurative meaning of the sonnet is its critique of the conventions of Petrarchan love poetry. Shakespeare employs a series of similes (comparisons that are a form of figurative language) that Petrarch and other poets often used to praise the ideal woman. These comparisons created the image of a woman who no real woman could ever equal, and the sonnet is therefore satirizing the way in which the love poetry of the time created images of the feminine ideal that no woman could ever achieve. 
In addition, some scholars have regarded the lines "I have seen roses damask'd, red and white, But no such roses see I in her cheeks;" as an allusion to the Wars of the Roses, a conflict between the Houses of York and Lancaster that took place between 1455 and 1487 over control of the English throne. The House of Tudor, founded in 1485, adopted the York and Lancaster Rose as its symbol after the Wars of the Roses, and this rose has red and white streaks. This sonnet was published in 1609, after the House of Tudor was no longer in power, but the sonnet may have been written before 1603, when the House of Tudor was still in power. 

Shakespeare's Sonnet CXXX is written as what is called a blazon, which is a literary poem that catalogs the characteristics and virtues of the beloved, while at the same time it mocks the Elizabethan conventions of poetry that praise love. In addition, it satirizes the Petrarchan sonnet that compares the lover to Nature in terms that seem hyperbolic.
Literal meaning
Literally, the speaker's lover is nothing like the women for whom sonnets and other poetic forms are usually written. Her hair does not flow in luxurious tresses; instead, it is as though"black wires grow on her head"; she has no rosy cheeks, and her breath "reeks." Nor is her voice mellifluous as "music hath a far more pleasing sound." And, when she walks she "treads on the ground." Yet, the speaker truly loves her because he feels that his love is more valuable than that of any poetic fancy because he loves her despite her flaws.
Figurative meaning
The anti-Petrarchan comparisons of the lover to various things lend humor to this sonnet. For instance, Shakespeare parodies the roses in the cheeks, eyes like sunbeams, perfumed breath, and walking on air. She has none of these or any other goddess-like attributes. Her eyes "are nothing like the sun," there is no "perfume" in her breath; it "reeks," and she "treads on the ground" rather than walks. She has no snowy white complexion or goddess-like attributes; yet, the speaker loves her dearly:

And yet, by heaven, I think my loveAs rare as any she belied with false compare (ll.13-14)

Any false comparisons for the sake of poetry, Shakespeare says figuratively, are meaningless. It is her unique qualities that endear her, not flowery metaphors and similes.