In a podcast episode 
, I looked at theories of metaphor, settling on Lakoff and company's conceptual theory of metaphor , but adding my own twist.
This page is a Starting Point.
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Lakoff's theory holds that there are metaphorical systems in the brain. A metaphorical statement like “that [statement] went right over my head” is literally false, but is interpretable because there’s a metaphorical system that acts as if human communication is packing ideas into containers (words or messages), shooting them over to a listener or reader, who then unpacks them and now has the original idea in her head. (This is called the Conduit Metaphor.)
In that metaphorical system, how objects and containers and physical movement behave is called the Target Domain. Communication is the topic of the Subject Domain. Importantly, when we have problems with communication, or we want to understand something new about communication, we primarily do the work in the subject domain:
* I have a problem with communication (in the target domain). * What's an analogous physical-world problem (in the source domain)? * How would I solve that problem there? * I now solve the target domain problem by translating over the solution from the subject domain.
These metaphorical systems are shared – more or less – among humans because (1) they’re frequently based on physical or social experiences we all share, and (2) we’ve spent our lives adjusting our mental or target domains to get along effectively in a world whose most salient feature is the people we interact with. We’re social animals, and social animals spend their time “tuning themselves” to each other.
I have a variant theory that I call the Kludge Theory of Metaphor, based on the notion that your brain, like everything in your body, is a gross kludge.