The song "Sing What You Can't Say" by Hoobastank is about the difficulty of expressing one's emotions and feelings to someone they love. The lyrics describe the struggle of the singer to let go and open up, to say those three little words that should say it all - "I love you". Despite the singer's efforts to express themselves, they feel like they never get it right and that "I love you" doesn't quite explain the depth of their feelings. The singer acknowledges that they are not the type to wear their heart on their sleeve and hopes that their silence is not mistaken for not caring. In the end, the singer decides to do what they can and sing what they can't say. They hope that by expressing themselves through music, their loved one will understand the depth of their emotions and feelings. Overall, the song is a heartfelt expression of the struggles and vulnerability involved in opening up and expressing love to someone else. The lyrics are relatable and emotional, making it a powerful and moving song.