"Am matter of" is a phrase that refers to something that is important or significant. The antonyms of this phrase include insignificant, trivial, unimportant, inconsequential, and irrelevant. Using antonyms to describe the opposite meaning of a word or phrase can provide a clear understanding of its usage in different contexts. For instance, when someone says, "I am matter of your existence," it conveys that their presence or absence holds great value. In contrast, saying, "You are not matter of my concern," implies that the person's actions or behavior are irrelevant and unimportant. Therefore, antonyms can be helpful in understanding the intended meaning of a phrase or word.