Figures of speech are defined as expressions that are used figuratively, that is, the words mean something other than what they mean when used literally. For example, a figure of speech is, "It's raining cats and dogs." Taken literally, this sentence would mean that when you look out your window, you will see cats and dogs falling from the sky onto your lawn and that your umbrella won't be quite adequate for the storm.... Taken figuratively, non-literally, this sentence means that the storm is a fierce one and the rain is coming down in great quantities. In this case, when you look out your window, you will a lot of rain falling from dark clouds and your umbrella may still be inadequate for the storm....
Figures of speech are formally called "tropes." As stated by Kenneth Burke in Grammar of Motives (Dr. Robert J. Belton, Creative & Critical Studies, University of British Columbia), there are four classic tropes. These are irony, metaphor, metonymy and synecdoche. Many other tropes (figures of speech) have been added to the classic four. Some are simile, personification, apostrophe, hyperbole, meiosis, puns, onomatopoeia, etc.
In "The Fall of the House of Usher," written in a first person narrator point of view, three examples of tropes--or figures of speech--that Poe uses are metaphor, as in "shades of the evening;" personification, as in "melancholy House of Usher" and "his speaking guitar;" meiosis, also called understatement, as in "I had so worked upon my imagination as really to believe that about the whole mansion and domain there hung an atmosphere peculiar to themselves...."
Metaphor is a comparison between two unlike things, for example as in "The cotton candy was heaven." Personification is giving human qualities to inanimate objects, for example as in, "The dark forest laughed at us." Meiosis is understatement, or making something sound less important or significant than it really is, for example as in "Seeing the approaching killer tornado made me uncomfortable."