LitCharts assigns a color and icon to each theme in Metamorphoses, which you can use to track the themes throughout the work.
Metamorphosis
Humanity vs. Nature
Love and Destruction
Gods and Humans
Time, Fate, and Poetry
Summary
Analysis
Unlike Achelous, Nessus the centaur is fatally wounded trying to compete with Hercules for Deianira. After defeating Achelous, Hercules travels home with his new wife Deianira. They come to a river that is flooding so high that it is nearly impassable. Nessus calls out to Hercules that he will carry Deianira across the river while Hercules swims across. Hercules trustingly hands Deianira to Nessus.
Nessus is another character who competes with Hercules over a woman. Nessus is a centaur—half person, half horse—but not endowed with any divine powers. As a result, Nessus is killed in his competition against Hercules, whereas Achelous the god only lost a horn.
Active
Themes
When Hercules reaches the opposite bank, he hears Deianira scream. Hercules screams that Nessus is a monster for trying to rape another man’s wife. He shoots Nessus through the chest with an arrow. Nessus whispers that Hercules will pay for killing him, then hands Deianira his blood-soaked shirt, telling her that it will excite her husband’s lust.
Even though Hercules has defeated Nessus, Nessus seems to be able to instigate revenge by giving Deianira a cursed shirt. This suggests that, even when one kills their adversary, they are not always free from the revenge that this person seeks.