Let’s look at some definitions and context. Metaphor is a tool that has been employed by artists of all types for centuries. The Concept is the thing we will express using a Metaphor. We’ll work backwards to the idea of conceptualization through examples or metaphors.
This book uses Metaphor and Image to refer to the poetic comparison used to communicate design ideas. Use of like and/or as is optional.
This is all about clarity of communication in a poetic and artistic medium. So, to go a bit further, a Metaphor or an Image is;
• An Implicit Comparison: language used to describe someone or something by means of a vivid comparison, not meant literally
• Figurative Language: using figures of speech or symbolism ...