Revenge as an obligation, not a choice
Orestes does not want to kill his mother for sport. He does it because Apollo commanded it and because the house of Atreus demands blood for blood. The play frames revenge as something imposed from outside, not freely chosen, which makes it harder to judge Orestes simply.
Divine command versus human guilt
Apollo's order gives Orestes cover, but the Furies do not accept that cover. They punish the act regardless of who ordered it. The play puts two systems of justice in direct conflict and does not declare a winner.
The corruption of the house
The house of Atreus has been poisoned for generations. Clytemnestra killed Agamemnon. Agamemnon sacrificed Iphigenia. Every crime in the family produces another. The play shows a household where violence has become the only inheritance.
Recognition and reunion
The scene where Electra recognizes Orestes is careful and slow. Aeschylus makes the siblings prove the connection to each other before acting. Recognition here is not just emotional; it is what makes the revenge possible.
Guilt that cannot be hidden
Clytemnestra's nightmare shows that guilt works on people even when they think they have moved on. Orestes's vision of the Furies at the end shows the same thing from the other side. The play treats guilt as something that surfaces whether or not you invite it.