Metaphor is from the Greek metaphora, meaning 'to transfer.'
In this case, to transfer meaning from one idea to another.
Whereas simile says that one thing is like another thing, metaphor says that one thing is another thing. It transfers the qualities of the second thing to the first thing, without drawing any separation between them.
Simile: The sun spills like a golden yolk across the rocks
Metaphor: The sun's golden yolk spills across the rocks
Simile: His laugh was like a shotgun
Metaphor: His shotgun laugh
Simile: Her smile was like a flash of lightning
Metaphor: Her lightning smile
Simile: Night fell like a dark cloak across the land
Metaphor: The dark cloak of night fell across the land
Remember that if a phrase has 'like/as' it is a simile, so a metaphor cannot contain 'like/as' to compare two things.
Some nice examples from literature:
...the music that can be produced by an orchestra of ideas. (The Labyrinth of the Spirits, Carlos Ruiz Zafón)
Now his face was a book written in a language long forgotten, in an alphabet unimagined. (The Graveyard Book, Niel Gaiman)
My heart was so light I could have flown. (The Binding, Bridget Collins)
His little pig eyes were crawling up and down her. (Pretty Little Dead Girls, Mercedes M. Yardley)
All the world's a stage, and all the men and women merely players (As You Like It, Shakespeare)
We switch off the light and open the big window because we both love storms - the dusty electric smell, the dark, spreading wings of clouds, the ecstatic drumbeat of rain. (Sister of My Heart, Chitra Banerjee Divakaruni)
Maybe the fear and nausea were no longer a sea to drown in but only a pool of water reflecting the past alongside the now. (Flowers for Algernon, Daniel Keyes)
We can check whether these are metaphors by reducing them to similes. Here, we are saying that:
Ideas can play music in the mind like an orchestra
His face was like a book
Your heart feels like it is weightless when you are happy
His eyes were like a pig's
The world is like a stage and people are like actors
Storm clouds have wings like a bird and rain sounds like a drum
Fear and nausea are like a sea or a pool of water
Metaphor is still about drawing a connection between two things you wouldn't ordinarily associate. Perhaps they share a similar colour, shape, pattern, sound, smell, emotion or behaviour. Combining them creates a stronger image than either one does by itself. A shotgun is one thing, a laugh is another, but a shotgun laugh could blow the room apart. The metaphor amplifies the imagery by combining those two things.
Have a go at finding a metaphor to connect these items:
A street and a snake
An animal and an annoying aunt
An insect and a party
A colour and an emotion
Next, try to come up with four more metaphors for anything you'd like.
If you would like me to check through your similes and metaphors from these two units and provide feedback, e-mail them to email@example.com with proof of payment for £10.