what are the 3 main themes of the poem
There is a certain timelessness to the poem.
You could argue that its messages about the abuse of power and the temporary nature of political authority are as relevant today as when Shelley was writing.
Shelley points out the arrogance of Ramses (also spelt Ramesses) and other leaders, whose power has led to pride and the mistreatment of others.
The sculptor satirises (uses humour or irony to criticise) Ozymandias, shown by the phrase, "the hand that mocked them...".
By describing how nothing remains of Ozymandias but a work of art (statue) and collection of words (inscription), Shelley suggests that art, language and literature are far more enduring (lasting) than human power.