What is the theme in The Metamorphosis by Franz Kafka?

Death is certainly a theme in this story. When Gregor dies, the family grieves momentarily. In their minds, their family member died on the day that he transformed, despite the efforts that Grete made to make him comfortable at home. Much like life with a severe disability, Gregor's condition was one that there was no returning from, and it didn't take long before they reached the limit of their tolerance for his condition.