He is beautiful when he is paying attention to little details. He should always be cautios and say that "good morning beautiful" or "how was your day"; with a phone call before something important or a flower left at the right place; with spontaneous actions; with her favourite chocolate and a sincere smile.
He is beautiful when he makes her smile. With good or bad jokes she will laugh no matter what. When he is acting like a dick (in convinient situations), when he makes compliments and comparisons that not even him understands them.
He is beautiful when he communicates. Very few men can talk about their feelings. But the way men don't know what women think, nor do women know what is going on in men's head.
He is beautiful when he knows and appreciates what he has next to him and when he is faithful. Through the millions of girls out there he finds one that is both beautiful and smart but doesn't make him feel the same like her. At that point he will realise his true feelings for her.
He is beautiful when he doesn't lie. He is beautiful because he has the courage to take the responsability for his actions and consequences. When he is caught lying, he will find all the possible reasons to explain himself and eventually blame her for his actions. That is called a coward and cowards are ugly.
He is beautiful when he wants to make her happy. When his happiness is to see her happy. That is a true sign that he really loves her.
He is beautiful when he helps her, when he hugs her even she is mad, when he kisses her goodnight even after a fight, when he lets her sing along with the radio and when he remembers little things.
But the most beautiful thing about him is when he loves her back.