In my view, it is being responsible, and caring, and true to his word (Integrity). He is protective of those who need it, and not self-serving or selfish. He is kind and caring for the needs of the less fortunate. He respects others. His character and his honor need to be evident in all he does, and says.
No man is perfect, or probably even close, but knowing that and admitting that helps keep him humble. He does what needs to be done, whether it's changing a diaper, cooking dinner, or just being a shoulder to cry on. He is confident in his masculinity without being macho. He knows how to take care of a woman, but not dominate her. He needs to let go of any inflated ego, and yet still be able to lead when called upon.
Lastly, he needs to get in touch with his emotions, but not be controlled by them. He can shed tears without feeling he is less of a man.