Michael is the key to the whole story and his daughter, Eve, is the key to winning the war.
It looks like there are many people who don´t like Michael. I was very surprised when I discovered this in the underworld club. So, What would be "Underworld" without Michael? It wouldn´t make any sense. Even in "Underworld Awakening" he is present although we, unfortunately, won´t see Scott Speedman playing Michael´s role.
He is the key because he is unique; The only one whose blood makes him capable of becoming half vampire, half lycan and more powerful than both.
Eve, his daughter, is the key to winning the war because she is as powerful as her dad; she is the unique hybrid child.
And, of course, Selene, our favorite Death Dealer, is as important for the story as Michael and Eve.
So "Underworld" wouldn´t make any sense without them. The three of them are the main characters.
Nevertheless, Michael was, is and will always be the key ♥ I´d say he is the "Symbol" of the Underworld movies ♥