Depends on the can. The "vintage military ration collection crowd" (yes, that's a thing) says that after decades you start to get some nasty leaching from can -

Depends on the can. The "vintage military ration collection crowd" (yes, that's a thing) says that after decades you start to get some nasty leaching from can -> food, especially if it's an acidic food product (e.g. tomato sauce). Nowadays, they coat the cans. But I'm pretty sure whatever tests the coatings go through aren't simulating 20+ years of storage.