As Gregor attempts to save his job by delivering a long speech to the Chief Clerk in Section One, Kafka describes the Chief Clerk's response with two similes:
And while Gregor was speaking he did not stand still one moment but stole away towards the door, without taking his eyes off Gregor, yet only an inch at a time, as if obeying some secret injunction to leave the room.[...] Once in the hall he stretched his right arm before him towards the staircase, as if some supernatural power were waiting there to deliver him.
The two similes here illustrate the complete communicative disconnect between Gregor and the Chief Clerk: while Gregor is attempting to eloquently defend his job (a speech the reader is privy to, but not the Chief Clerk), the Chief Clerk backs away "as if obeying some secret injunction to leave the room." The Chief Clerk is acting as if he is responding to a command that is completely unintelligible to Gregor or as if responding to a "supernatural power" equally beyond Gregor's comprehension. This underscores the horror of Gregor's visage, which is so terrifying it forces the Chief Clerk to move away as if compelled by the divine. In Kafka's fiction, the world often operates in confusing ways that leave the protagonists at the whims of others: Gregor's life is no different. In fact, Gregor will never know why or how he transformed into a bug, nor why he is so horrifying as an insect.
Kafka uses two similes to describe the Chief Clerk's reaction to seeing Gregor post-metamorphosis:
He was still carrying out this difficult manoeuvre, with no time to observe anything else, when he heard the chief clerk utter a loud “Oh!”—it sounded like a gust of wind—and now he could see the man, standing as he was nearest to the door, clapping one hand before his open mouth and slowly backing away as if driven by some invisible steady pressure.
The Chief Clerk—Gregor's employer—is the first person to see Gregor after he transforms into a large insect. Kafka uses two similes to describe the Chief Clerk's reaction: the first one compares his loud gasp to "a gust of wind," while the second one describes the Chief Clerk backing slowly away "as if driven by some invisible steady pressure." Both similes then compare the horrified response of the Chief Clerk to something natural, whether it's the wind or some invisible force of nature. This suggests that people can not help help but be driven away by Gregor's new body, somewhat justifying the terrified reaction of those who see Gregor. In a way, these similes contribute to the story's sense of futility: Gregor can't help but become an insect, but the other characters equally can't help but be repelled by his insect-like body.
When Grete and Gregor's mother try to clear out Gregor's room in Section 2, they catch sight of Gregor perched on the wall in an ironic perversion of nature:
[...] caught sight of the huge brown mass on the flowered wallpaper, and before she was really conscious that what she saw was Gregor screamed in a loud, hoarse voice: “Oh God, oh God!” fell with outspread arms over the sofa as if giving up and did not move. “Gregor!” cried his sister, shaking her fist and glaring at him.
The image of Gregor perched on the "flowered wallpaper," and the ensuing horror that image evokes in Grete, is an ironic perversion of an otherwise natural scene: a bug perched on a flower. The fact that it is a human-sized bug perched on flowered wallpaper, however, distorts this otherwise natural scene.
The situation is further ironic because it results in Grete addressing Gregor directly for the first time since his metamorphosis, and yet she does so in a situation in which Gregor appears most like a bug. Gregor crawling on the side of the wall, on top of a wallpaper flower, and evoking horror in his sister and then mother is the most inhuman he has appeared at this point in the story. However, it is only now that Gregor's sister addresses him by name.
Gregor's mother is described as falling on the sofa "as if giving up." While the simile is used to describe her fainting, it specifically highlights that Gregor is losing any chance of communicating with his family as he becomes more insect-like. They are "giving up" on finding a way out of this terrible situation, a fact that becomes clear in the third section of the story. The simile also emphasizes once more the horror that is Gregor's inhuman appearance, as it provokes Gregor's mother to figuratively give up on life itself.
Kafka uses a simile to describe the haste with which Grete opens the window when she enters Gregor's room in Section 2:
[...] and as if she were almost suffocating tore the casements open with hasty fingers, standing then in the open draught for a while even in the bitterest cold and drawing deep breaths.
Grete tears open the window "as if she were almost suffocating" and opening the window will provide her with much-needed air. Grete ostensibly needs to open the windows because Gregor’s room smells bad, and opening the window alleviates the smell by letting in fresh air. The fact that Grete opens the window "even in the bitterest of cold" emphasizes how terrible being in Gregor's presence is, as being in Gregor's room without an open window is far worse than braving the cold. In fact, even in the cold she stands there "for a while," deeply breathing in the fresh air.
The simile comparing Grete's actions to those of a person who is suffocating suggests that Gregor's room is uninhabitable: it is literally not fit for sustaining human life, and in fact it slowly kills that which is human. The simile then emphasizes what the reader already knows—that an existence confined to one room is stifling and inhumane. The simile also implies that Gregor is less-than-human, or at the very least that the human part of him is dying off as he remains trapped in the room. The lack of music in Gregor's life—which is a stand-in for art, culture, and other forms of mental stimulation that make life worth living—is brought to the forefront later in the short story when he becomes entranced by Grete's violin. For now, the depravity of Gregor's impoverished existence is merely hinted at through this description of Grete's actions and her feeling of suffocating.