For example:

In the opening of the poem, the speaker uses a visual image that is also a simile to compare a dream deferred to a raisin. The speaker asks the question, “Does it [the dream] dry up/Like a raisin in the sun?” (2-3). The raisin, which used to be a moist, taut, healthy-looking grape, has shriveled up to become a raisin. Why compare a dream deferred to a raisin? The appearance of the raisin isn’t emphasized, so the description isn’t as significant as the simile. Like a raisin, a dream deferred shrivels up and turns dark because the sun has baked it. Here the sun is emphasized because it stresses time since time is measured by the sun’s movement. Also, like the raisin, the dream has been on hold for a long time; consequently, it has transformed into something very different than it once was. Because raisins look so different, few people would believe that raisins were once grapes unless they’ve been told accordingly. Similarly, a dream that continues to be postponed will go through an evolution as well–it won’t be the same as the original. The speaker emphasizes that a raisin “dr[ies] up” or loses its life-giving moisture. The comparison of the dream to the withered raisin shows how a dream that is postponed changes dramatically and will not turn out as the person originally intended.

Ultimately, Hughes uses a carefully arranged series of images that also function as figures of speech to suggest that people should not delay their dreams because the more they postpone them, the more the dreams will change and the less likely they will come true.

I hope this helps you. I teach high school English.