My first impression after reading Metamorphosis was that Gregor's transformation into a vermin was somehow a metaphor for a soldier coming home and dealing with post traumatic stress.  It is mentioned that Gregor was a soldier, and now in a job he does not like as a travelling salesman, and the first lines mention that he woke "from troubled dreams."  He turns into an entirely different being from what he was when he went to sleep, and his family does not know how what to do about his new state of being.  At first, his parents shun him while his sister tries to take care of him, but when it becomes apparent that he will not be turning back to the human he once was, even her nerves begin to fray.  The story culminates with Gregor's family members deciding that his presence is ruining them because he cannot understand them and they cannot communicate with him (though if they had tried, they would know this is not so), and that he must go.

We are presented this story from the perspective of Gregor, who had no control over his transformation, and no way to change back.  He is aware of his surroundings and understands what his family says, though they cannot understand him.  He becomes cut off from them and nobody knows how to fix it.  It just made me think of someone who comes home after experiencing things their family cannot imagine and being cut off from them, unable to explain what is going on in their head anymore, leading to family tension and pain.