The primary element of figurative language in the poem is that of irony. All that remains of the great "works" of this "king of kings" is the remains of the monument Ozymandias had ordered to be carved in his own image, a reflection of his egotism. Ozymandias once taunted the "Mighty" to look upon his power and "despair." All that remains of his empire, however, is a decaying "colossal wreck," broken and half-buried in the "lone and level sands" that "stretch far away." The contrast between the arrogance of Ozymandias' words and the seemingly endless emptiness surrounding his "vast and trunkless legs of stone" emphasizes the poem's irony.
Figurative language allows poets and writers to express concepts in unusual ways, making associations where ordinarily there would be no connection. Simile, metaphor, personification, alliteration, hyperbole and so on are all used to make descriptions and create images in the mind's eye. By using figures of speech, readers can get a visual picture of what the author or poet wants to express.
In "Ozymandias," Shelley very quickly destroys any sense of grandeur surrounding the statue. The mocking tone confirms the irony in the words inscribed on the stone. Nothing lasts forever, not even the perceived sense of worth of "Ozymandias, King of Kings." By using figurative language, Shelley is able to create sharp contrast between what Ozymandias may have perceived would be the benefit of his statue and the reality of the situation, wherein his pride in his "works" reveals nothing more than a "colossal wreck." Hyperbole in the use of "colossal" allows the reader to imagine the sheer scale of destruction—far more than just a statue but a whole empire.
Shelley continues to explain the magnitude of the apparent loss of Ozymandias's kingdom by using alliteration, a sound device, evident in the words, "boundless and bare, The lone and level sands stretch..." This adds emphasis to the endlessness and uselessness of the situation in which the statue now lies and helps Shelley confirm his message. Shelley delivers a warning that no matter how "mighty" a person considers himself to be, the danger is that he will be reduced to nothing more than "trunkless legs of stone." How much better would it be to be remembered as a man of compassion rather than to be remembered for "a sneer of cold command."
There is element of personification, although the poem is about the statue of a man.
There is also element of irony and of some hyperbole.
The voice of Ozymandias is heard as an overarching arrogant and omniscient (all-knowing) voice, giving even more irony to the destruction of his statue.