Antigone's primary reason for wanting to bury Polynices is that it's in accordance with divine law. Once someone dies, their body isn't supposed to be just left to rot out in the streets; they must be buried according to the appropriate funeral rites. Such rites don't just pay homage to the deceased individual but to the gods themselves, so in defying Creon's order and seeking to bury Polynices, Antigone believes she's acting in accordance with the will of the gods.
