Bears are incredibly strong and resilient creatures.  If they want to get into something they typically can.  The key is to make your trash less desirable for the bear.  Some have suggested spraying vinegar or a pepper solution in the trash will make it so the bear will move on. This can be painful to do, every time you are putting trash in.  A more effective method is to secure the cans with Trash Lockers.  These straps with side-release buckles are permanently attached to the trash cans and act as a true deterrent.  Generally, the bear will spend a couple of minutes fighting with the secured trash can and then move on it easier food.