The line from The Metamorphosis shows us that although Gregor has changed into an insect, he still has human thoughts and emotions. He can still think and feel like a human and appreciate the finer things in life, such as music, which would presumably be lost to him if he were solely an animal, especially an insect. So the line shows that although he has physically changed, mentally and emotionally he’s still a human.
Gregor’s role as a son and brother also undergoes a transformation along with his physical transformation. Prior to his transformation, his entire family is dependent on him and his job. However, after his transformation, he becomes dependent on other members of his family for his sustenance and survival. For example, in the initial days after his transformation, Grete feeds him, and he comes to depend on her for nourishment.
Gregor struggles with a number of identity issues in his new form. Although he has been transformed into an insect, he still has human feelings and sensations. However, being an insect, he cannot find a suitable outlet to express his feelings and emotions. The few instances in which he tries to reach out to other people or experience pleasure, as when he wants to hear Grete play the violin, he’s vehemently dismissed because of his repulsive form.