A metaphor is an expression which says one thing is a thing which it is not.

• It is, in a way, a LIE. 
• Phrases can have both a LITERAL and METAPHORICAL meaning.

My dad’s going to kill me.

But the word “kill” is a lie.

The word comes from the Greek μεταφορά which means to “transfer” over.

• The boys were glued to the television.
• Here, the word “glued” is a lie. But we transfer the idea of not moving, being stuck, to the boys watching the television.

• She had a heart of stone.
• Here, the word “stone” is a lie. But we transfer the idea of not having any feelings to the woman.