What is an example of an extended metaphor in Paul Lawrence Dunbar's "We Wear the Mask"?

Dunbar's poem is especially relevant today as new ways to "wear the mask" keep appearing. In carefully framed selfies, or in funny Facebook posts, or in well-executed snaps and tweets, we wear the mask: that is, we show the world a certain version of ourselves that may not be exactly who we really are.

So that brings us to the one and only extended metaphor in Paul Lawrence Dunbar's "We Wear the Mask," and it's right there in the title. The mask is a metaphor for that carefully crafted and false version of ourselves that we present to the public, in order to hide our true thoughts and feelings.

You can call this mask an extended metaphor because it gets mentioned over and over. That is, Dunbar doesn't just mention it one time. He puts it in the title, and then he mentions it three more times: once in every stanza. In fact, describing the mask, and describing how it's different from our true selves, constitutes the entire length (and the purpose) of the poem.

Let's take a closer look. 

First, the title. Notice that it's not "I Wear the Mask" or "She Wears the Mask." It's "We Wear the Mask." The implication is that everybody does this: everyone, at some time or another, puts on a false "face" to show the world.

Next, the opening stanza. The speaker describes the mask as a thing that "grins and lies," meaning it offers a smile to people while hiding the truth. This mask "hides our cheeks," meaning it keeps our true expressions from being revealed, and it "shades our eyes," meaning it keeps our most expressive facial feature (the eyes) hidden so that they can't reveal what we're really thinking. But on the inside, hidden beneath the mask, we have "torn and bleeding hearts."

Now let's look at the second stanza. The speaker asks, hypothetically, why everyone else should pay attention to what makes us sad and frustrated. No, the speaker says. Let people only see us when we've got that mask on. He means, let's keep our "tears and sighs" hidden: the things that make us feel sad or frustrated, let's keep them out of sight, beneath the mask.

Finally, the third stanza. The feeling gets even more intense here as the speaker builds toward an explosive ending for the poem. We smile on the outside, even though we're privately crying out to "great Christ" from our "tortured souls." And, even though our hardships are difficult and long-lasting, we sing. All this fake singing and smiling lets the world get a better impression of us than we really would project if we did share our darker feelings and thoughts, the speaker hints. He rounds out this final stanza with one more assertion: "We wear the mask!" Yes, this time with an exclamation point.