He could feel the anger 'boiling up' inside him. [=he could feel himself becoming very angry]
The water in the pot is 'boiling over'. = The pot (of water) is 'boiling over'.
The kettle (of water) is 'boiling'. = The water in the kettle is 'boiling'.
(..) - You. Don't even think about it. I hope this turns out better than your plan to cook rice in your stomach by eating it raw and then drinking boiling water. This plan's nothing like that plan. - How? - 'Cause this one's going to work. Keep moving. Ah, my old enemy... (..)2011 Kung Fu Panda 2