Compare how both poets present their main subject in "Sonnet 130" and "Ozymandias."

Both poems use a central conceit—the idealization or aggrandizement of the human form—to make a point about art and humanity, although their tones are very different. Shakespeare is reacting against (or even satirizing) a tendency in poetry to use hyperbole to idealize female beauty; he contrasts the idealized language used to describe women with the truth about his lover (culminating with the hilarious “And in some perfumes is there more delight / Than in the breath that from my mistress reeks.”). Shakespeare’s poem is funny, but concludes with a serious sentiment: “And yet, by heaven, I think my love as rare / As any she belied with false compare.”
Shelley’s poem is not funny. Here, it is the ancient King, Ozymandias, who has idealized himself by creating a giant statue of himself. Whereas Shakespeare’s point is to poke fun at poetic hyperbole, Ozymandias truly does believe in his own greatness: “My name is Ozymandias, King of Kings; / Look on my Works, ye Mighty, and despair!” Even though the ruined sculpture retains some of the grandeur of the king, Shelley’s point is that even the great works of Ozmandias will erased by time—even something as colossal as the statue.
Both poems make a point about the relationship of art to truth. The difference is in attitude. Shakespeare recognizes that poetry can never capture what he values in his lover; his poem succeeds because it rejects any artistic attempt to describe her beauty. Ozymandias, on the other hand, seeks to make the statue into a kind of permanent symbol of his omnipotence; it is as if he would command art to be faithful in the same way he commands his sculptor. Shelley, with Shakespeare, recognizes the impossibility of that goal; in Shelley’s case, the poem ends on an almost existential note: “‘Nothing beside remains. Round the decay / Of that colossal Wreck, boundless and bare / The lone and level sands stretch far away.’”

Shakespeare's "Sonnet 130" and Shelley's "Ozymandias" deal with different subjects, yet use a similar conceit to convey their themes.
"Sonnet 130" is a romantic ode, and the subject is the beauty of the speaker's paramour. The opening line, "My mistress' eyes," begins the description, and the rest of the poem is a list of subsequent attributes. Ozymandias, on the other hand, is political in nature. The speaker recounts the description of a statue he heard about while traveling; it is the fallen statue of a king with an intimidating epigraph.
The conceit or primary literary device of both poems is a central image: a human idol. Shelley presents his statue in the form of a literary postcard, a ruined statue recounted from a faraway land. Shakespeare generates the image of an idealized beauty that his lover, ironically, does not live up to.
Both poems use the central image to create irony. Shakespeare's list of hyperbolized beauty traits (coral red lips, breasts as white as snow) serves to illustrate how ludicrous such expectations are of female beauty. Similarly, Shelley's fallen statue underscores the hubris of the king unwilling to acknowledge the inevitability of his own demise.