What are some themes of Antigone?

Arguably the most important theme of the play is the conflict between human law and a higher moral law set down by the gods.
The law of Thebes, as laid down by Creon, says that Antigone's brother Polynices was a traitor whose body should be left to rot. The higher moral law to which Antigone adheres with equal insistence says that Polynices, whatever he's done, should be buried according to established customs in honor of the gods.
It's this central conflict that generates much of the play's action and sets the scene for an epic battle of wills between the resolute Creon and his equally stubborn niece. Creon is determined that earthly law should prevail, the law that he as king of Thebes has decreed in the time-honored fashion. As for Antigone, she's no less determined to see a higher morality win out, a cosmic justice established by the gods that operates at all times and in all places, irrespective of the circumstances.