to be as incompatible or irreconcilable as ice and hot coals; describes two opposing parties that cannot coexist or tolerate each other

ice and charcoal cannot be held in the same container; fundamentally incompatible elements or people cannot coexist

incompatible as ice and charcoal; used to describe people or ideas that are fundamentally opposed and cannot coexist

ice and coal do not speak, yet it is obvious which is cold and which is hot; means that one's true nature or sincerity is apparent without needing to be stated