When I last visited my grandmother I found a couple of expired cans of peaches. Given that they should have been consumed three years ago I don't think it's safe to eat them.
I was thinking about using them for composting but I don't know if it's safe for the plants. What can I do with expired food instead of just throwing it away?
To add to Chris' answer, I'd say eat them after doing the usual look-, smell- and taste-checks. Above all, make sure the can hasn't been deeply dented, is rusty or is bulging; in those cases, don't even taste-test it: the severity of botulism (or any other illness originating from bacteria in preserved food) is just too serious to take the risk (and, talking about sustainability: imagine the environmental cost of treating serious infections and their consequences that need several days, if not weeks, of hospitalisation).
If you do not eat them, composting those will be completely fine, but you might want to remove the excess liquid first if your compost heap is humid enough already. Some processed/cooked/rotten/mouldy food is fine in composts, especially if they represent a small part of it. The most important thing is to make sure that your compost has the right C:N ratio, the right aeration and the right humidity.
Make sure you recycle the cans. You can also "upcycle" them by poking a few holes in them and using them as plant pots, which might contain some of that compost at some stage...
Eat them.
Then look into what the different types of expiry date mean. Tins, dried pasta and many other foods have a best before date based on guesswork about quality. Most foods sold chilled and some others have a use by date based on safety. I won't try to convince you to ignore use by dates though I don't always stick to them myself. Display until dates are about stock control and nothing else.
Back to your peaches: if the tin is bulging or they seem in any way "off" then compost them. Even mouldy veg is fine for composting.
More/less related How food producers calculate "best before" date?: eat it if it looks good - expiration date is just best wish of producer, food may be perfectly fine after expiration date.
You can try to use it for plants if it was not expired so long ago. check the expiry date and the information given to make sure that there is nothing that harms plants.
