Shut Up is the opening track on the album Still not getting any... and it's a very powerful song.
It's about not taking crap from anyone, that I am me and no one else. It's the song that says be yourself and not like everybody else, because what is a life if you're not living your life?

To start the day with Shut Up is a very good way, because then you'll have it in you from the begining, don't take crap from anyone.

Simple Plan – Shut Up! - Domestic Album Version