Gregor's physical form parallels his inner state. At first, Gregor is shocked and awkward in his new body. He has a hard time getting used to his many, skinny legs or his lack of teeth. However, with time alone in his room, he is able to start walking easily. He becomes comfortable in his new form.

The moment his parents see him fully is when he begins to deteriorate. His father physically abuses him, injuring him in ways from which he is unable to recover. He bleeds from being thrown across the room and gets an infection when an apple, thrown at him by his angry father, lodges in his "flesh" and starts rotting. Gregor is in constant pain from his untreated injuries and starts refusing food. Eventually, he wastes away and dies.

Gregor's emotional state during his transformation moves from shock, confidence, and then finally to despair. When he was gaining control over his new body, he had some hope of acceptance, but once his family rejects him, Gregor gives up any attempt to adjust to his new circumstances. He similarly gives up any hope of continuing to live, unable to deal with the pain and the alienation of his life.

At the beginning of the story, Gregor wakes up to find that he now has an "armour-like back," and a "brown belly, slightly domed and divided by arches into stiff sections." He also has "many legs" which are "pitifully thin." A little later in the story, when trying to get out of bed, Gregor notices that his new legs are very difficult to control. When he manages to move one leg as he wants, "all the others seem to be set free and ... move about painfully."

As the story progresses, Gregor seems to slowly adapt to his new body. He finds that his back is "more elastic than he had thought," and he begins to use "the adhesive on the tips of his legs" to hold himself upright. He also notices that, while he may no longer have teeth, he does now have a "very strong jaw." Gregor also learns to control all of his legs, so that they do "exactly as he (tells) them."

The moment in the story when Gregor starts to adjust to his new body is also the moment when his family see it for the first time. They are of course horrified and disgusted, and his father gives him a "hefty shove" which sends him flying, and leaves him "heavily bleeding." The next morning Gregor's left side seems "like one, painfully stretched scar," and one of his legs appears to be broken so that it "drag(s) along lifelessly." Later his father throws apples at Gregor, and one becomes "lodged in Gregor's flesh." Because of such injuries as these, Gregor begins to lose "much of his mobility."

Towards the end of the story, Gregor resigns himself to the reality of his situation. He becomes used to "his entire body aching." The pain in fact seems to get "weaker and weaker" and "finally disappear(s) altogether." Soon Gregor can't even feel the decaying apple lodged in his back. His head sinks and the "last breath flow(s) weakly from his nostrils," and Gregor dies.

The changes to Gregor's body throughout the story reflect his changing emotional state quite closely. At first his body is completely new, and his emotional state is, understandably, one of shock and confusion. As he then begins to adapt to his new body, he becomes calmer, and a little more confident. Just at this moment he dares to show himself to his parents. They retreat in disgust and injure him in the process. It is at this point that Gregor becomes scared again, and begins to lose what little hope he had of being accepted by his family. This new emotional state, of abject hopelessness and sadness, is reflected by the injuries he sustains, and by his consequent immobility. The eventual death of his physical body is synonymous with, and inextricable from his emotional death.

As we all know, Gregor Samsa fully turned into a giant, "monstrous vermin." This is, essentially, the biggest physical transformation that he goes through in the book. Interestingly enough, however, he doesn't seem to be particularly shocked or surprised about his newly acquired body form, nor does he wish to know why the change happened; in fact, he immediately tries to adapt to his new lifestyle as an insect and doesn't try too desperately find a way to transform back into a human. He soon realizes that some tasks are harder to do—like sleeping, for instance—but he also learns that he very much enjoys climbing and crawling on the walls.

The minor physical changes he goes through after his transformation, such as the brown liquid that comes out of his mouth whenever he hurts himself or the changes in his physical appearance, are usually metaphorical and symbolic. Thus, it's safe to say that his confusing physical transformation and metamorphosis does affect some aspects of Gregor's life, but his personality and his emotional state remain constant throughout the book; he never truly loses his humanity, and he still does everything out of love for his family. Unfortunately, his family is disgusted and repulsed by him, and they are embarrassed of his existence. Samsa fails to understand that he only lived to work and provide for his family and realizes that the only way to please his family is to die. Thus, he stops eating and eventually dies, unceremoniously and alone, similarly to how he lived.