A figure of speech is a way of expressing yourself so that what you are saying is not literal, meaning not using words that reflect reality. Metaphors and similes are figures of speech, and I will give you some examples of each. Then we can look at ways to use them in your life.
A metaphor is saying something is something else, in a way that makes the reader or listener understand that the quality of the something else reflects some "truth." For example, if I say, "He is a rock," I am not saying that the person is literally a rock. I might be saying that this is a strong person I can count on. Or I might be saying this is someone who just stands there saying nothing, like a rock. I might say, "Her smile is sunshine." We know that a smile cannot be sunshine. But what we take from that is that the person has a warm and glowing smile, just like the sun. If we say "It's raining cats and dogs," we know that there are no cats and dogs dropping from the skies, but that it is raining really hard. These are all metaphors.
A simile is an expression in which you say something is like something else, usually using the word "like" or "as," a comparison. So I might say "Her smile is like sunshine." Or I could say, "He is like a rock." The reader or listener will get the impression of sunshine or the quality of a rock from my simile. I could say,"I am as happy as a lark." That tells the reader that I am so happy I could be singing like a lark.
You can see now that our language is filled with figures of speech, and you have probably been using many, using them frequently, without even realizing it. When you explain something in terms of something else, whether in a metaphor or a simile, you are using figures of speech. You might want to describe a friend or a classmate in terms of something else, for example, as a flower or an animal like a fox. These might convey an image of colorful beauty or slyness. You might describe your feelings this way, perhaps saying, "I am as hungry as a wolf." When you are writing, you can use figures of speech in a way that gives your readers a wonderful picture of some kind. When I read or hear these figures of speech, they always give me an image in my mind. We want our readers and listeners to have images in their minds that make our meaning clearer, and that also makes for a more enjoyable experience.