"A man is charming."
Translation:남자는 매력이 있습니다.
이/가 join onto the subject of the sentence IF the sentence doesn't follow up after another
Example "남자(가) 여자 없습니다" The man is not a woman, let's say that the sentence started the conversation.
If we used the sentence mid-conversation, it would change to: "남자(는) 여자 없습니다" The man is not a woman
는 would be used because the particle is "comparing".
So, to answer your question, 매력 is an adjective. So it does not get 이/가 & 는/은 added to the word.
I don't think the part with the adjective 매력 is correct. 남자는 매력이 있습니다 literally means "the man has charm" and not "the man is charming", right? This would make sence, because then, of course 매력 would be a noun (charm) and it would be logical to give it a subject marker (이). I could be wrong, but since 매력이 is correct, this would be an explanation. Also, 있다 means something similar to 'has', so my explanation would make sence. But I'm not a native korean speaker, I'm just learning, so I'm not sure if I'm right :)