Naturalistic symbolism
The unique, almost mixed metaphorical style of Aeschylus provides him enough freedom to intermingle utilize solar and lunar cycles, night and day, storms, winds, fire, among other natural symbols to represent the vacillating nature of human reality: good and evil, birth and death, sorrow and happiness.
Character foiling and doubling
It is valuable to compare and contrast one character with another in this play since, like most of its complex symbolism, the characters are made to embody certain antithetical qualities that inevitably come into conflict. For example, Agamemnon is blind where Cassandra can see.
Fire and sunrise
Here Aeschylus captures the central tension of the play (between human and divine will) in a very specific image: the image of the fire at Troy versus the imminent sunrise. We remember that the signal comes at night, and much is made of how like that fire is to a sunrise, the dawn of a new day. Yet the fire at Troy is one of destruction; it is mortal, mundane, and human. On the other hand, the sunrise belongs to the gods and to nature. We might think of the bonfire as a "false" dawn, since Agamemnon's return only brings Argos more sorrow and pain.
Women as promiscuous
Helen, Clytaemestra, Cassandra are all three adulterous women. There is a certain amount of emphasis placed on the natural weakness woman in play. It is mainly the Chorus, however, a group of old men, who advance this position. The women themselves are quick to point out their innocence, although, there is also much ambiguity in their reasoning as well.
Womanliness and Manliness
This brings up the idea of ancient Greek social structure and the socially determined roles of men and women. Clytaemestra's manliness should be given close attention. Alternatively, there is an over-masculine quality to Agamemnon in his apparent love for war, a love so strong he sacrifices his female daughter for the sake of his campaign.
Premature death
Several portents and symbols indicate the importance of the theme of premature death, the death of youths. In fact, it probably hearkens back to the ill-fate house of Atreus and Thyestes' being tricked into eating his own child. Iphigeneia, daughter of Agamemnon and Clytaemestra, is sacrificed as a maiden, and a whole generation of young Argive men have been lost fighting in Troy.
Ambition and daring
One of the human flaws discussed at length in the play, ambition or daring is the sin of Agamemnon, the one for which he must inevitably pay with his life.
Divine versus human justice
Possibly the most important theme in the play, justice is left as one huge question mark when the curtain falls on Agamemnon. Clytaemestra makes a case for her own innocence, but is highly doubtful that the gods have sanction the joy she took in killing her husband. The Zeus calls out to Zeus many times to no avail. What they want to know is, was the murder of their king divinely caused or an act of base vengeance.
Beast symbolism
Generally the domain of portent and prophecy, animal symbolism plays a subdued but essential role in the play. The symbol of the lion that tears apart its host, the eagle who lets its fledglings die, the wolf, the cock and his hen, all of them provide metaphors for major characters. One especially important beast symbol is the hare tore out of the woman, which symbolizes Iphigeneia's sacrifice. Humans who forget how to govern themselves justly tend to be personified as beasts.
Corruption and purity (healing)
Here one should think of the curse on the house of Atreus. The original impurity in the house still has not been cleansed. The blood of innocent children has brought sorrow Argos, and there are many questions as to who will finally clean it up, that it may heal.
