"
along if you feel like a room without a roof
Because I'm happy
Clap along if you feel like happiness is the truth
Because I'm happy
Clap along if you know what happiness is to you
Because I'm happy
Clap along if you feel like that's what you wanna do
Hey, come on
(happy)
He is also explaining a certain joy that he feels, and that he wants everyone to join in, forget your worries for just a moment, to clap along, and to just have fun. He is also asking you, "Do you know what happiness is? Do you feel happy? If not, Just sing along, open your heart."