Rhetorical devices are techniques that writers use to persuade, create a literary effect, or evoke an emotional response from the reader.
Whenever you describe something by comparing it with something else, you are using figurative language, which is any language that goes beyond the literal meaning of words in order to furnish new effects or fresh insights into an idea or a subject (e.g. Whenever you call something “cool,” you’re not talking about its temperature but referring to some other quality it possesses).
Analogy: A comparison made between two things or situations in order to make a point.
In a sense we've come to our nation's capital to cash a check. When the architects of our republic wrote the magnificent words of the Constitution and the Declaration of Independence, they were signing a promissory note to which every American was to fall heir. This note was a promise that all men, yes, black men as well as white men, would be guaranteed the 'unalienable Rights' of 'Life, Liberty and the pursuit of Happiness.' It is obvious today that America has defaulted on this promissory note, insofar as her citizens of color are concerned. Instead of honoring this sacred obligation, America has given the Negro people a bad check, a check which has come back marked 'insufficient funds. (Martin Luther King, Jr., “I Have a Dream,” Aug. 28, 1963)
Metaphor: A comparison of two unlike things using any form of the verb “to be” (am, are, is, was, were).
The streets were a furnace, the sun an executioner. (Cynthia Ozick, "Rosa") But my heart is a lonely hunter that hunts on a lonely hill. (William Sharp, "The Lonely Hunter")
Simile: Comparing two unlike things using “like” or “as.” Saying one thing is similar to another.
Life is like an onion: You peel it off one layer at a time, and sometimes you weep. (Carl Sandburg)
Symbolism: The use of one thing to represent