Is it safe to freeze canned foods?

No. Cans of food should not be frozen. When cans of food become frozen, the fluid inside expands distorting the shape of the can and affecting the integrity of the seams allowing microorganisms to enter. The danger would be when it thaws - microorganisms could then grow.

There's no reason to freeze cans of food and canned foods should be stored and shipped so that freezing is avoided.

If you are referring to freezing food that has been removed from the can, e.g. leftovers, yes, it would be safe. Realize that the texture of the food may be affected.

For instance, freezing portions of pureed tomatoes from a #10 can could work well. Doing the same thing with baked beans can result in a mushy texture.

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I found out today that you can freeze previously (storebought) REGULAR canned beans by rinsing all that gook off of them, putting them in a airtight container, and pouring water over them - being sure to leave enough head space to allow for expansion. When ready to serve, let thaw naturally in the fridge then use as normal.