So, when you are asked to describe something you haven't seen, you take things you have seen and put them together in a new and incongruous way. So, if you tell me that our tax system is fair, I could respond in several ways. No, it's not fair. I as I know them. For example, I swallow and you swallow food and drink.
All humans do.
And you certainly know what yukky medicine tastes like, and you hate to have to swallow it. That's a metaphor. My statement is more powerful and memorable than yours, I think. Figures of speech, then, can turbocharge the power and effectiveness of language we use in speech and in writing. Go for them.