Metaphor

All the world's a stage,And all the men and women merely playersThey have their exits and their entrances
William Shakespeare
A metaphor is a figure of speech that says that one thing is another different thing. This allows us to use fewer words and forces the reader or listener to find the similarities.
The word metaphor comes from the Greek word metapherin (meaning "transfer").
The simplest form of metaphor is: "The [first thing] is a [second thing]."
Look at this example:
Her home was a prison.
In the above sentence, we understand immediately that her home had some of the characteristics of a prison. Mainly, we imagine, she could not leave her home. She was trapped inside. Why it was a prison we do not know, but that would be clear from the context--perhaps her husband forced her to stay at home, perhaps she was afraid of the outside. We don't know, but the rest of the story would tell us. What is important here is that in five simple words we understand a lot about her environment, how she felt and how she behaved. In this sentence, "prison" is a metaphor.
Look at another example:
George is a sheep.
What is one characteristic of sheep? They follow each other. So we can imagine that George is a follower, not a leader. In this sentence "sheep" is a metaphor.
Metaphors are very common in everyday language. But poets also like to use metaphors. In the following famous verse (from The Highwayman by Alfred Noyes), can you spot three metaphors in the first three lines?
The wind was a torrent of darkness among the gusty trees,The moon was a ghostly galleon tossed upon cloudy seas,The road was a ribbon of moonlight over the purple moor,And the highwayman came riding--Riding--riding--The highwayman came riding, up to the old inn-door.
Look at these examples of metaphors with sample sentences and meanings: