Ozymandias

Irony is the use of words to convey a meaning that is the opposite of its literal meaning
Comic irony: irony that is humorous (whereas much irony is not)
Dramatic irony: When the audience (or reader) knows a fictional character is making a mistake, because the audience has more information than the character. Dramatic irony is used when an incident occurs whose significance the audience understands but the characters do not.
Tragic irony: In tragic irony, a character's actions lead to consequences that are both tragic, and contrary to the character's desire and intentions.
Historical irony: A kind of situational irony that takes a long period of years for the irony to become evident.

The speaker recalls having met a traveller “from an antique land,” who told him a story about the ruins of a statue in the desert of his native country. Two vast legs of stone stand without a body, and near them a massive, crumbling stone head lies “half sunk” in the sand. The traveller told the speaker that the frown and “sneer of cold command” on the statue’s face indicate that the sculptor understood well the emotions (or "passions") of the statue’s subject. The memory of those emotions survives "stamped" on the lifeless statue, even though both the sculptor and his subject are both now dead. The whole area around the wrecked statue was covered with flat sand.The once-great king’s proud boast has been ironically disproved; Ozymandias’s works have crumbled and disappeared, his civilization is gone, all has been turned to dust by the impersonal, indiscriminate, destructive power of history. The poem remains primarily an ironic and compelling critique of Ozymandias and other rulers like him, but it is also a striking meditation on time-bound humanity. In this poem Shelley attempts to highlight the true value of language and poetry. Ozymandias makes the point that language has an immortality which other art forms do not. It is for this reason that Shelley also asserted 'all high poetry is infinite...durable, universal and permanant'.

Irony in the poem-Ozymandias was a megalomaniac. He had illusions of grandeur. The ancient king is presumptuous enough to exhort onlookers to view his ‘works’ which have long since dissolved into dust. The statue, which was a symbol of his power, was once great. But now it is a ‘colossal wreck’. The pharaoh and his legacy are supposed to be immortal but the very symbol of his legacy has collapsed and is being swallowed by the desert.

Transience- Ozymandias is a metaphor for the ephemeral nature of political power. The poem is obsessed with transience and impermanence. The statue is a symbol of Ozymandias's ambition, pride, and absolute power, and thus the poem implies that kingdoms and political regimes will eventually crumble, leaving no trace of their existence except, perhaps, pathetic statues that no longer even have torsos.

Pride- In the inscription on the pedestal Ozymandias calls himself the "king of kings" while also implying that his "works" – works of art like the statue, pyramids, that sort of thing – are the best around. Ozymandias thinks pretty highly of himself and of what he's achieved, both politically and artistically. The fact that he commissions this "colossal" statue with "vast legs" points to his sense of pride, while the statue's fragmentary state indicates the emptiness (at least in the long term) of Ozymandias's boast.

Message- Shelley attempts to convey except nature that nothing and no one is immortal. Time is great leveller. With the passage of time everything becomes equal to everything else. Kingly authority and symbols of power are annihilated in due course. Power is not a constant variable.
It is linked to the transient nature of life. All human power shall be obliterated in time and all the arrogance that such power generates in those who hold it is misplaced.