Metaphor is an implied simile. Here a word or expression that in literal usage denotes one thing is applied to a distinctly different kind of thing for the purpose of suggesting a likeness between the two. Metaphor does not, like the simile, state that one thing is like another or acts as another, but it takes that for granted and proceeds as if the two things were one.
•Life is a dream.
•Variety is the spice of life.
•Revenge is a kind of wild justice.
Note that every simile can be compressed into a metaphor and every metaphor can be expanded into a simile. When we say, “Her eyes were like diamonds” we use a simile, but when we say, “Her eyes were diamonds” we use a metaphor.
•O my Love’s like a red, red rose. (Simile)
•O my Love’s is a red, red rose. (Metaphor)
•He fought like a lion. (Simile)
•He was a lion in the fight. (Metaphor)
Not only nouns, but other parts of speech may also be used metaphorically. In the following example, the verb is used metaphorically.
•How sweet the moonlight sleeps upon this bank. (Merchant of Venice by Shakespeare)
In a mixed metaphor an object is identified with two or more different things in the same sentence. When used inadvertedly, the effect can be ludicrous.
•I smell a rat, I see it floating in the air, but I will nip it in the bud.