In a survival situation you could find yourself without a can opener ans possible your knife. If you get your hands on some cans of food here is how to get them open with just your hands.
In this how to video the CrazyRussianHacker show use the steps to popping open a can of spinach. He starts by denting in the middle side of the can with his thumbs. He then locks his finger together then repeats the same on the other side. The slowly workes around the can until he can tear it open.
I try to keep a Survival Kit Can Opener in my bug out pack to avoid this but if your hands are all you have just give it a go.