To me, I think Joyce is trying to get across in the story that without passion and love, you are "dead." There is no meaning or hope in your life that you get up for in the morning. Because Michael died for his first love Greta, he is actually more alive than anyone else in the story. The others just go through life without really finding something worth dying for. Then you are truly living.
1. There are many references to the dead.
Page 1946- Kate and Julia's brother Pat
Page 1971- Michael Furey
Page 1973- Aunt Julia
1948- Gabriel's mom Ellen
1961- Monks who sleep in a coffin
1963- Gabriel's speech
1966- Sad Irish song that Michael sang about a drowning mother and her child
2. The names Michael and Gabriel are also archangels. In the story, Michael was Greta's(Gabriel's wife) very first love. He died visiting her in the rain right before she left and she was broken hearted. Gabriel just now found out about him when Greta got upset after hearing a song he used to sing. In the bible, Michael is the head archangel and Gabriel is subservient to him. This kinda shows that Greta will never feel the same way about Gabriel as she did Michael, because she never really got over him.