An idiom is a phrase that when spoken outside of a particular culture it seems incomprehensible. This peculiar use of phrases is not taken literally but is understood by members of that culture. A phrase such as “jump the shark.” is an idiom. It doesn’t mean to literally jump the shark, it means when a show or radio program has reached the impending inevitable end. Using this term is appropriate when others understand the terms meaning. It would be inappropriate to use idioms in cultures where the meanings of the words are challenging and hard to understand.
Analogies use comparison to highlight similarities between two or more things. They are often using to clarify issues. Here’s an example of an analogy Hot is to Summer as cold is to winter or the famous Forest Gump analogy says “life is like a box of chocolates because you never know what you're going to get.” That’s the function of the Analogy; it is drawing a comparison in order to show similarity in some respect. Analogies are a good way to help get your point across. But if the analogy is unclear, it hinders instead of helps.
Take two unlike things, compare them and show that the have something in common and you have a metaphor. According to Thinking, “A metaphor carries another meaning with the original or carries the original meanings beyond into a new meaning. “ Ride to live and live to ride is an example of a