Let us remember that a metaphor is an example of figurative language, that compares one thing to something else completely different but forces us to see the comparison. However, metaphors differ from similes in that they assert a direct comparison without the words "like" or "as," that are always a characteristic of similes. Examining this great story then, we see that metaphors are uses to describe the veil that Mr. Hooper dons and its effect on those who see him. Note how Mr. Hooper himself, when he is having his interview with his fiancée, describes the veil as a "dismal shade," comparing what is just a simple layer of crepe to something more menacing and threatening. Note how this is repeated again in the text:
On a nearer view, it seemed to consist of two folds of crepe, which entirely concealed his features, except the mouth and chin, but probably did not intercept his sight, farther than to give a darkened aspect to all living and inanimate things. With this gloomy shade before him, good Mr. hooper walked onward...
Here, again, the veil is compared to a "gloomy shade," which, in spite of the way that the veil is described, gives it a greater, more sinister significance than the actual simplicity of the veil suggests.