In Orwell's short story "Shooting an Elephant," a British police officer stationed in Lower Burma succumbs to peer pressure from the native people and shoots a harmless elephant against his will. Moments before firing his rifle, the British officer experiences an epiphany and recognizes the futility of colonial oppression. Orwell writes,

For it is the condition of his rule that he shall spend his life in trying to impress the "natives," and so in every crisis he has got to do what the "natives" expect of him. He wears a mask, and his face grows to fit it. I had got to shoot the elephant.

The mask the British officer wears refers to his reputation as a resolute, callous master who is unsympathetic and always in control of every situation. As an agent of the colonial regime, the British officer recognizes that he must always maintain a certain disposition, even if it means acting against his will in order to uphold his expected standard. For example, the British officer understands that the elephant is no longer a threat and that he should simply wait for its mahout to return. However, he also knows that he must behave a certain way in front of the native people, who expect him to kill the beast.

The mask creates an internal conflict in the officer, who wrestles with his conscience and struggles to live up to the expectations of what his job demands. When the officer wears the symbolic mask, he behaves like a callous enforcer and his character will eventually change, transforming him into a new man. By continuing to perform and act like a resolute oppressor, the British officer will become the person he pretends to be on an everyday basis.

In Orwell's opinion, becoming a colonial master means that you have to wear a mask in terms of the role that your perform and also how you are perceived. In this essay, he realises that the crowds of people that have turned up view him as a kind of magician who is going to put a show on for them. However, the problem with this mask is that you have it on for so long that when you try to take it off you realise that your face has actually changed or grown to fit the mask itself, and therefore you can't actually remove that mask any more.

Since your question asks for a personal opinion, I'll give you my opinion of what this statement means. You have to interpret it in its context:

Here was I, the white man with his gun, standing in front of the unarmed native crowd--seemingly the leading actor of the piece; but in reality I was only an absurd puppet pushed to and fro by the will of those yellow faces behind. I perceived in this moment that when the white man turns tyrant it is his own freedom that he destroys. He becomes a sort of hollow, posing dummy, the conventionalized
figure of a sahib. For it is the condition of his rule that he shall spend his life in trying to impress the "natives," and so in every crisis he has got to do what the "natives" expect of him. He wears a mask, and his face grows to fit it.

The narrator represents Imperial Britain, and as such the people expect him to behave as their caretaker. At the beginning of the story, the narrator says that many people hate him, "the only time in my life that I have been important enough for this to happen to me." They hate him for the tyranny that he represents, but they turn to him for help in a crisis. That is what Orwell means when he says that "when the white man turns tyrant it is his own freedom that he destroys."

Orwell uses this metaphor to describe transformation. He means that he has forced himself to act a certain way, to be a certain person that is not who he thought he was. Eventually if we act a certain way we run the risk of actually becoming that person and that is what he is saying. If you wear a mask, if you act like someone you're not, then you will grow to fit, you will become that person whether you like it or not it's almost out of your control if you aren't careful.

Note: a metaphor is a figure of speech in which a comparison is made where one thing is used to designate another making an implicit comparison.

In "Shooting an Elephant," what does "he wears a mask, and his face grows to fit it" mean?

In Orwell's classic short story, he examines how imperialism negatively affects the ruling authority figures as well as the oppressed, marginalized Natives. In the story, a young British officer stationed in Lower Burma is given the directive to handle a situation involving an escaped elephant. As the British officer walks throughout the town searching for the loose elephant, a crowd of Burmese civilians begins to follow him. When the British officer finally discovers the elephant, it is peacefully grazing in a composed manner. The British officer, who is holding a powerful elephant gun, has no intention of shooting the elephant. However, the officer experiences an immense amount of peer pressure from the Natives, who expect him to shoot and kill the tranquil animal. At this moment, the British officer experiences an epiphany regarding the nature of imperialism by saying,

I perceived in this moment that when the white man turns tyrant it is his own freedom that he destroys. He becomes a sort of hollow, posing dummy, the conventionalized figure of a sahib. (Orwell, 8)

The officer goes on to say that the agents of ruling imperialist regimes are required to metaphorically wear a mask, which grows to fit their faces. The metaphorical mask refers to the resolute, callous appearances that agents of the imperialist regime must maintain at all times. The British officer is essentially forced to act against his own will by shooting the elephant in order to be perceived as a resolute, intimidating figure of British imperialism. The metaphorical mask suppresses the imperial agents's individuality and forces them to behave and appear a certain way that represents the powerful regime, which explains why their freedom is destroyed when they turn into tyrants.

In "Shooting an Elephant," what is the significance of the line about wearing a mask?

This line expresses the narrator's feelings about the role he plays in being part of the colonial government in Burma. In fulfilling his position as a member of the police force, he is required to be someone he is not and to enact policies with which he does not agree. He feels imprisoned himself by the political and social forces at work in the colony. By way of example, he shoots an elephant that does not need to be destroyed because his position in the village has forced him to do so. Even though he is armed and in uniform, he feels endangered by the native crowd that has gathered, and he fears their reaction if he does not kill the elephant as they expect him to do. Going against his own nature and conscience, the narrator destroys the animal. He is changing to "fit the mask" that he wears as a part of the colonial power structure.