The moral of The Metamorphosis is that being made to bear an outsize burden of obligation lead to alienation and dehumanization. Gregor Samsa is a traveling salesman who works to support his parents and sister, and he has been worked so hard that he has essentially had to forego all of the things that make human life worth living. He works so much that his mother even feels angry that he does nothing much outside of work and sit at home, even though his work is all for his family’s benefit.

Gregor himself is aware that he has no real life. He is always traveling for his job, and so he eats bland and unsatisfying food on the road—food from which he reaps no enjoyment. He feels completely exhausted and is frustrated with the fact that he has no time or opportunity to cultivate real, intimate relationships. This is evidenced by the fact that the beautiful picture frame on his wall contains a photo of a woman that he clipped from a magazine; he does not actually have a real-life person whose picture he can put in the frame. His family, meanwhile, are free to enjoy luxurious meals, leisurely days, and the pleasure of each other’s company.

Gregor cannot even sleep enough to ever feel truly rested and has to wake up at a ridiculously early hour just to be at work on time. The one day he doesn't make it in, the manager comes to his house to guilt him into emerging from his room when it is clear that there is something very wrong with him. Gregor’s only purpose comes from working on his family’s behalf, and once he can no longer do so, he completely loses relevance and importance in his own home.

After his transformation, Gregor loses more and more of his humanity as his family treat him less and less like a relative or even a person. His transformation into a giant insect emphasizes how little he was able to enjoy ordinary human life even when he had a human form, as well as how little thought his family gave him beyond what he was able to provide for them. Where once he placed all his time and energy into fulfilling a perceived obligation to his family, Gregor now becomes an unwanted burden to them. Rather than bear that burden, however, Gregor’s parents and sister ultimately leave him behind in pursuit of their own happiness.