Opened a can of soup and it made a loud noise with the open-tab lid suddenly pulling in.
I know that bacterial decay can make cans bulge (due to gaseous byproducts of bacterial metabolism) and the general rule is that bulging cans or cans that expel a large amount of gas on opening should be discarded.
However, are there any known dangers associated with negative pressure in a can that implodes enough to pull the can lid in on opening? There are relatively few types of bacteria that consume gases (an example being nitrogen-fixing bacteria in legumes).
The can wasn't visibly deformed or damaged in any way before or after opening.