How to distinguish between metonymy and metonymy?

Metonymy is a metaphor. The two things that are compared and used for comparison have similarities, but there is no correlation. Therefore, even if there is no metaphor "image" between ontology and vehicle, the word "image" can be added and replaced by simile. Metonymy is to replace the things to be expressed with related things. There is no similarity between ontology and borrowing, only correlation, so the word "image" cannot be replaced by simile. For example, the "perfect fly" in "A warrior with shortcomings is a soldier after all, and a perfect fly is just a fly after all" is a metaphor for those reactionary guys. In simile, it can be written in the form of "reactionary guy is like a fly". In One Hundred Years of Weakness and the Eight Years' Anti-Japanese War in Yan 'an, "Fighting" and "Yan 'an" are metonymic, and "Fighting" represents War of Resistance against Japanese Aggression and "Yan 'an" represents China's * * * production party. This is to replace abstract things with concrete things, which cannot be replaced by similes. It would be a joke to use the expression "War of Resistance against Japanese Aggression is like a war" and "China's * * * production party is like Yan 'an". They can be replaced because ontology and borrowing are closely related: fighting is a weapon and is related to war; Yan' an is a revolutionary holy land, which is related to China's * * * production party. You didn't explain my question.