What metaphors are used in Seven against Thebes by Aeschylus?

With the deaths of Eteocles and Polyneices, the curse of Laius (that the city would be destroyed if he fathered any children) is metaphorically fulfilled. In classical times, and in classical writing, a city's ruler was often a symbol of his city: in other words, Eteocles was Thebes, and so was Polyneices, who was to have been Eteocles' co-ruler. Therefore, with their deaths, the city also dies (metaphorically).