Out of all the things Gregor could change into, he changes into an insect. Gregor’s life was actually very similar to the one of an insect. Most insects, especially ants and bees, have some sort of workers that provide for the rest of the group. Gregor provides for his family in much the same way as an insect would provide for its nest or hive. He sacrifices almost all aspects of fun, and does not desire to do anything but work. Eventually, his income becomes less of a generous act, and more of an expectation. His family's existence rests solely on his shoulders, just as a queen bee relies on the worker bees. Thus, with this extended metaphor, Kafka criticizes society behaviours, showing the true nature behind all of us.
Secondly, the story also appears to be a metaphor that describes communication in Gregor’s family. As Gregor's paychecks become increasingly more expected, his family begins to view him as less of a person, except for his sister. When Gregor does not awake in time for work, his mother first informs him that he will be late. She does not become worried about something being wrong until a little later, and even then she only appears to be concerned because he will miss the train. Gregor and his family do not communicate very well; his frequent business trips the likely cause. He even remarks to himself about the "quiet life his family has been leading," an allusion to the fact that little conversation occurs among them. Spending so much time away at work alienates Gregor from his family, and further objectifies him as a paycheck rather than a member of the family.
Kafka in this novel also explores some different symbols. Kafka places great emphasis on time in the novel. Gregor first wants to catch the 5 a.m. train as usual, but then realizes that he has slept until 6:30. He thinks about catching the 7 a.m. train, but isn't sure he can get up in time. When the chief clerk arrives only a short time after the company has opened, Gregor is angered that suspicion is build on him for wasting only an hour of the firm's time. The passage of time on the clock face is shown also by the changes taking place outside, as morning fog gives way to clear light, something Gregor notes as the previously hidden hospital across the street comes into view. Time, of course, symbolizes the capitalist order in which time is money and is thus valuable. Oversleeping is a crime because by oversleeping Gregor misses business and thus wastes money. Gregor's mother, speaking with the chief clerk, notes that Gregor thinks of nothing but work and never goes out in the evening. This shows the extent to which the rule of the modern economy weighs down on Gregor: time that is not spent working is useless time, and any activity that is not work is pointless.
Moreover, Kafka also uses pathetic fallacy to illustrate Gregor’s death. As Gregor dies at the precise moment when the sun comes up. He sees the first light of dawn and dies. Hence here this new sun, illustrates a new era, where the Samsa’s will not have a “bug” in their family. The symbol of the sun also appears at the moment Gregor has just discovered his had transformed himself into a bug. So, the light, symbolizes Gregor's love for his family and his discovery of his humanity. Hence, Kafka leaves this poignant ending, in order to make people horrified by the way his family treated him, and consequently react to this feeling.
We see that, Kafka through this extended metaphor, wanted to make his readers realize that there was a greater truth in existence. The parabola of this metamorphosis, prepares us to react in the right way, when we are faced with the truth. And that life distracts us from what really matters, but we have to focus on allowing this truth to be seen.