IT WILL RAIN - BRUNO MARS

This song is about love, romantic love. He's afraid that the girl, someday, could leave him and break his heart. He also says that she would remember all the sacrifices he's doing for her, and that anything couldn't save him from his sad feeling.

He compares the clouds and the dark sky with his feelings, what he would feel when she'll walk away: "Cause there'll be no sunlight if I lose you, baby. There'll be no clear skies, if I lose you, baby. Just let the clouds, my eyes will do the same if you walk away... Everyday it will rain."

There's a problem, and it is that he's never going to be her mother's favourite, but that he'll try to get her, and his father too, because what he really wants is the girl's love.
And it's always the same, he continues saying that if he loses her, he won't be okay.