Is cooking beans or any other food in metal cans safe? Occasionally, I go camping and cook beans over a fire inside of the [what I am assuming is tin] can it comes packaged in (after opening the lid).   Does heating the metal can release any chemicals in the food?   Is it safe? 

I usually have the top of the can open and stir it frequently.
The interior of modern cans are a heat resistant plastic (remember they pressure cook the cans at the factory), and will be fine for heating liquid things

Just don't try using it to fry stuff!