Prometheus is portrayed as a rebellious and proud god despite his humiliating punishment at the hands of Zeus's underlings, Strength and Violence. Punished for his acts of compassion toward humanity, he shows compassion for the suffering of others, notably the suffering of the mortal Io. He may be too arrogant for his own good. Several characters urge him to act more humbly and avoid inducing Zeus's wrath, but Prometheus refuses, and repeatedly criticizes Zeus's tyranny and ingratitude, right up to the end when he provokes Zeus's anger into action.
Although he does not appear on the stage at all, Zeus is a major character in the play, as he is continually in the thoughts and speech of the characters on the stage. Having only recently defeated his father Cronos, and the other Titans, Zeus is the new ruler of Olympus. He rules with an iron fist and completely without compassion or understanding for his subjects. The audience sees the results of his tyranny by seeing the behavior of Zeus's thuggish henchmen, Strength and Violence, by witnessing the suffering endured by Prometheus and Io, and by noticing the fearfulness in the attitudes of Hephaestus, Oceanus, and the Chorus.
The Chorus of Oceanids represents the prevailing attitude of the average citizens in ancient Greek society. They are people who adhere to moral norms, which in this case means obeying and fearing Zeus. Their attitudes stand in contrast to that of Prometheus, who remains defiant throughout the play. Although they show sympathy for Prometheus, they urge him not to arouse Zeus's anger. Interestingly, at the very end of the play, they remain with Prometheus despite the threat of violence from Zeus.
Hephaestus is ordered by Zeus to shackle Prometheus to the cliff and impale him with an adamantine wedge. He hates the fact he must use his skills to do this job, and he weeps as he does it, all the while being taunted and threatened by Strength. His assessment of Zeus as a harsh ruler probably represents the views of his fellow deities.
Apparently sent to discover the details about the marriage Prometheus boasts will lead to Zeus's downfall, Hermes appears at the end of the play, immediately browbeating and insulting Prometheus. As Zeus's messenger, Hermes seems to represent the attitude of Zeus, in stark contrast to Hephaestus. Hermes seems to be saying exactly what Zeus would say if he were onstage.
The presence of Io in the play brings up interesting comparisons to Prometheus. Both are suffering because of actions taken by Zeus, but while he is bound here and cannot move, she has been driven here by the gadfly, and cannot stay in one place. Unlike Prometheus, who knows exactly how long his torture will endure and how it will end, Io is tortured by not knowing when her suffering will end. As a suffering human, she is an example of the creatures upon whom Prometheus took pity, which led him to be in his current situation. The one service the shackled Prometheus can do for Io is to use his insight to tell her of the end of her suffering, which will indirectly lead to his own rescue.
In terms of his attitude toward Zeus, Oceanus is neither as bitter as Hephaestus nor as sycophantic as Hermes. Oceanus is an example of a subject of Zeus's rule who believes in getting along without invoking the tyrant's rage. Clearly, Oceanus believes one can talk oneself in and out of trouble. On the one hand, Oceanus admonishes Prometheus for speaking in such a way as to stir up Zeus's wrath; but he also tells Prometheus he will try to soothe Zeus with his words.