Metaphor is metaphor, that is, using concrete, vivid and well-known things to explain abstract, unfamiliar things or profound truths, so as to make your expression more vivid and clear. These two rhetorical methods both focus on the similarity of two things. Metaphor is a rhetorical format, which generally consists of three parts: ontology (what is said), vehicle (what is used for comparison) and metaphor (words used to connect ontology and vehicle). Metaphor requires that ontology and vehicle must be essentially different things, and they must have similarities. "Metaphor" is not as formal as metaphor in use, and we use it more in spoken language.