Result From Badly Stored Canned Food. Store your cans off the ground Leaving your canned food on the ground exposes them to condensation floods and temperature changes. If the dent is large enough that you can stick your finger into it it should not be eaten.
Shelves are your friend. You should not see the top of your cans dome up even in the slightest. Bulging cans must be thrown out even a slight bulge is a very bad sign.
They do not have the taste of freshly cooked foods.
If the liquid covering the veggies inside the can has a milky appearance do not eat it. You can tell if a canned food has gone bad by first looking at the outside of the can. How to tell if canned food has gone bad. Canned goods are supposed to basically last forever right.