A simile or metaphor is a comparison or equalization of two dissimilar things made through language.

The two requirements for language are: that its signals (words) be arbirtrary (unrelated to their object) and conventional (accepted and upheld by all users).

A requirement of language, then, is that there be nothing “rose-like” about the word “rose.” That any other word, given convention, would work as well.

The phrase, “My love is like a red, red rose,” then, becomes: “My love is like something that is nothing like a rose.”