His parents, no longer supported by him financially, are so repelled by his transformation that they completely ostracize their son. Even his sister, when her brother becomes a social pariah withdraws from him, despite his former support for her violin-playing. At first she feeds him and then gradually grows hardened as he resembles less and less the brother she once knew. At the end of the story, the family is relieved upon Gregors passing, and instead plans for his sisters possible marriage, rather than mourns the loss of the man who sacrificed his life so they could be happy.
Gregors fantastical fate is thus a metaphor for a very realistic condition — someone who is imprisoned in a miserable life, with ungrateful relatives, and no real secure sense of a happy and fulfilling identity.
Similarly, Lu Xuns “Diary of a Madman,” in which the title madman is haunted by the phrase “Eat people” and eventually becomes convinced that all of the individuals around him are cannibals, including the medical establishment trying to cure him, could be seen as a metaphor for working-class oppression, or simply the dog-eat-dog nature of human life. An unreal scenario conveys with more intensity a very real but often hidden truth about life..