Hint: It starts with an "m"
http://literary-devices.com/
The figurative language used in the phrase "it's hard to see the pain behind the mask" is metaphor. A metaphor is a figure of speech that implies a comparison between unlike things, suggesting that one thing is another. In this case, the speaker is comparing the pain someone is experiencing to a mask. The literal meaning of the sentence would be that it is difficult to perceive or understand the pain that someone is hiding or concealing. The metaphorical meaning is that the pain is not immediately visible or apparent, just like a mask hides one's face. By using this metaphor, the speaker conveys the idea that it takes effort or insight to recognize the emotional suffering that someone may be going through.
