The Poskim discusses whether one may open cans of food and other containers on Shabbat. For example, may one open a tuna fish can or container of juice? Does this constitute a violation of the Melacha of "Soter"-dismantling/destroying? Hacham Ovadia in Halichot Olam (Ch.4) and Hacham Bension in Or Lesion permit doing so, on condition that one does not intend to keep the container, but merely to remove the contents and discard the container. In such a case, these vessels are similar to what the Gemara refers to as "Mustaki"-insubstantial, disposable containers that when torn open, are not significant enough to be considered a violation of "Soter."
SUMMARY
It is permitted to open cans with a can opener on Shabbat, provided that the can is discarded after removing its contents.
