It's too late to get that can of cranberry sauce open in time to save Thanksgiving, but you should still learn how to open a can without a can opener so you'll be better prepared next time. In a delightful 2013 YouTube video (via Cosmopolitan), internet personality "Crazy Russian Hacker" helpfully explains how to open a can without any tools at all. This is, of course, a practically timeless skill — with all the disruption going on in the world, regular old metal cans are still a pretty common object.
Spoiler alert: you do need one thing, and that's a concrete surface. Basically you just turn the can (or "tin" for you Brits) upside down, place it flat against the concrete, and rub the top surface repeatedly back and forth against the concrete. This scrapes off the thin top layer of metal that was previously forming the lip of the can and creating the seal between the body of the can and the separate piece of the lid. When you think you've rubbed enough metal off, flip the can over and give it a little squeeze. If it's ready, that will be enough to dislodge the lid piece — no can opener required.
I have some concerns about using this concrete method for opening cans that contain mostly liquids, because the can will become leaky while it's still upside down. Also, maybe it's too cold or just too embarrassing to go outside to do this. Don't worry, you can also open a can with a knife like this.
You can also use a spoon! Hope it's a sturdy one though, and it'll take some elbow grease. Hopefully all your effort makes whatever's inside that darn can taste even better than usual.