This is a bit of a tricky question, because “existentialism” itself as a unified body of thought is notoriously difficult to define. In reality, it refers to a diverse group of writers and artists addressing similar themes and questions in their work, often in conversation with one another, over the...
This is a bit of a tricky question, because “existentialism” itself as a unified body of thought is notoriously difficult to define. In reality, it refers to a diverse group of writers and artists addressing similar themes and questions in their work, often in conversation with one another, over the span of several decades. That said, we can define several of the terms referenced in the question and examine what relevance they have to Kafka’s novella.
The first is the notion of “existence preceding essence.” This refers to a concept explored in existentialist metaphysics. From the Greeks onward, Western philosophers worked from the assumption that in all things, there existed both an “outer” and an “inner” nature. Different thinkers used different terms (like “substance” versus “accident”), but the distinction held more or less throughout the centuries. Think of it this way: a glass of tap water has a list of observable attributes (appearance, temperature, etc.) that distinguish it from an ice cube, but they are essentially alike. A coffee table may receive a new coat of paint without losing its “table-ness.” Its essence or substance is what can be said to be inherent in the thing itself. It comes first; it is “primary.”
The existentialists pointed out that this categorical view of the world is insufficient when applied to human beings. They argued that human existence is a process of “self-making.” The “self” is better understood as a constructed composite of a lifetime of thoughts, actions, and interactions in the world. It is contingent, mutable, and always in a state of becoming. In other words, the fact of existence creates the product of essence.
So when Gregor wakes up to find himself metamorphosed into a hideous creature, he comically responds with the concern that he will be late to work. He is still acting and thinking as though he is “essentially” Gregor, the traveling salesman. As the plot continues, of course, he loses this identity, becoming increasingly insect-like in his thoughts and behaviors. “Gregor Samsa”—the industrious man, son, and brother—fades away entirely, leading us to question how real (or inherent) any of it ever was in the first place.
Another topic mentioned in your question is that of free will. The problem of free will was central to many existentialists. Albert Camus considered the point from the perspective of suicide: as human beings, we have the freedom to end our own lives at any moment. We can reject any choice offered us but almost always choose not to do so. In order to cope, we retreat into the mindset that our thoughts and actions are rational responses to a difficult but ordered world. The dimly-felt awareness that you are ultimately freely consenting to whatever horrible circumstances you find yourself in at a particular moment produces a sense of angst.
We are all free, but we are at the same time all enslaved. Kafka explores this by giving us Gregor’s internal monologue, in which he is shown to be constantly engaged by thoughts of duty to his employer and to his family. Gregor has so completely alienated himself from his own free will that almost everything he does proceeds from a sense of obligation. He has voluntarily surrendered his own freedom and refuses to admit it to himself. To reject one’s free will is to reject one’s own humanity, a concept made literal in Gregor’s transformation from man to insect.
In the existentialist view of things, the contradictions pile up. We live in a world without inherent meaning, but we continue to live nonetheless. We feel at all times constrained by circumstance, but every waking second we continue to affirm our consent to remain in that circumstance. This is what Camus referred to as the fundamental absurdity of life. To depict such a world, one must write an absurd story. So Kafka does just that: a traveling salesman becomes a giant cockroach; an unemployed man wearing an absurd blue work uniform kills his son with an apple.
So, while it would not be strictly correct to call The Metamorphosis an “existentialist novella” (the term did not exist yet), it would be fair to categorize it along with Hamlet, Crime and Punishment, and Bartleby, the Scrivener as belonging to a literary tradition which took up many of the same themes that would later engage the existentialists. Keep in mind also that this response is meant to be a kind of primer, rather than an in-depth exploration of these terms as they pertain to a rich intellectual tradition. Different thinkers have used these terms in different ways, and they often contested or outright rejected each other’s work. Nevertheless, this should provide some basic insight into what people mean when they refer to the “existentialist qualities” of The Metamorphosis.