"The Mask" is comprised of alternating lines between 2 speakers. One speaker hides behind a mask, and the other speaker wants her to show her true identity (we'll assume she's a woman for this answer—the poem assigns no gender to either speaker). The first speaker claims that he has to know whether this woman loves him or hides behind deceit in order to lead his emotions astray. She claims that it was the mask (or the deception) which first captured his mind. After all, she concludes, as long as the two have passion, the matter of whether she loves him or is deceiving him really isn't important.

One central theme is that people sometimes present a particular version of themselves to their lovers and may hide their true character. We know that this woman hides behind a metaphorical mask. She refuses to reveal her true inner character and, in fact, uses "gold" and "emeralds" to distract her lover. Does she hide behind wealth? Vanity? Interestingly, she believes that this deceit is what first captured the affections of her lover:

It was the mask engaged your mind,
And after set your heart to beat,
Not what's behind.

She claims that he doesn't love her because of her inner character, so she has no reason to put down her mask.

The poem is comprised of 3 stanzas of 5 lines each. The first, third, and fourth lines are written in iambic tetrameter. The second and fifth lines in each stanza are written in iambic dimeter. It is in these shorter lines that much of the complexity of the poem is contained:

Love or deceit.
Not what's behind.
In you, in me?

The poem follows an A-B-A-B-A rhyme pattern.

In this poem, the male persona wants the female he is talking to to take off the mask of self that people put on for the outer world. He wants her to reveal her true soul to him. He doesn't ask, but commands her in the first lines to "take off that mask of burning gold."

The woman refuses, saying he is "bold" (too aggressive) in wanting to know if her heart is "wild and wise," rather than cold. But the man persists, wanting to know if the woman is truly loving or deceitful behind her facade. The woman holds her ground, saying it was her mask or facade that attracted him and that he shouldn't look too deeply behind it. If they feel a spark of outward attraction to each other, a "fire," they should focus on that.

The poem is an exploration of appearance and reality. The male wants to know what is behind the woman's beautiful, fiery facade. The woman, feeling vulnerable, wants to protect her interiority. She knows the man has been attracted by her "mask" and wants to protect her soul from scrutiny. 

"The Mask" is divided into three five line stanzas. Each stanza follows an ABABA rhyme scheme. The poem is in the form of a dialogue between a man and a woman.

The poem “The Mask,” by William Butler Yeats comes from his collection of poems called "The Green Helmet and other Poems."  "The Mask" is about a conversation between a woman and a man. At the beginning of the poem he asks the woman to remove her mask so that he can decide if she is sincere or just a fake.  Her reply is that he is so taken by the mask that she doesn’t want to risk him seeing her.  She then asks him if it really matters to him if he discovers who she is behind the mask as long as there is love between them.  Yeats had been intrigued by the internal self and the external self for a long time.  This poem is a reflection of those questions.  He wanted to know who a person was and why they chose to hide behind certain “masks.”  In this poem the woman is simply reminding the man that what drew him to her was the “mask” in the first place, and not what lay behind the mask.  Yeats wrote about masks several times, including an essay included in a book called “Per Amica Silentia Lunae (1918)”

 "I think all happiness depends on the energy to assume the mask of some other life, on a re-birth as something not one's self."

The style or form of the poem is a more abreviated style and in dialogue form rather than strictly based on rhyme.

"The Green Helmet characteristically shows a tremendous advance in precision of imagery and syntax as well as an increased use of personal and contemporary themes. Yet along with the substitution of a hard, dry manner and lively, homely detail for the dreamy vagueness of the early poetry, the symbolism that he was evolving becomes more and more esoteric and obscure."