Households tend to have a designated lid opener who's usually the person with the strongest hands. When a lid is screwed on too tight, screwed on the wrong way or just plain stuck, that person's job is to open it, and the person gets an extra dose of appreciation by doing it without any external aids. Even that person, however, occasionally comes across lids that won't succumb to brute force.
When this happens with new, unopened jars, it's usually because the vacuum created when the jar was sealed needs to be broken. When it happens with jars of partially used food, especially honey, it's either because the contents of the jar are spread around inside the lid and are acting like glue or someone overtightened the lid or screwed it on the wrong way.
If your Magic Bullet lid won't come off, it's often because you were in a hurry when you leaded the blender and neglected to straighten the lid before screwing it on. That's usually the reason your NutriBullet lid is stuck, too.
Get a Grip on a Plastic Top With a Rubber Glove
Some plastic tops are just too wide to grip comfortably and your hand slips before you can develop enough torque. Improve your grip by putting on a heavy-duty rubber glove, which also protects your hand in case anything happens. If you need a really good grip, wear a rubber glove on each hand so you can get a grip on the jar as well as the lid.
Run the Lid Under Hot Water
When a lid on a partially used jar is stuck, it could be glued shut. If you can't loosen it using a rubber glove, turn on the hot water and let it run until it reaches its maximum temperature. Hold the lid under the water for about 30 seconds. Thankfully, you're still wearing rubber gloves, so you don't have to worry about getting scalded.
The hot water usually melts the hardened sugars holding the lid, and that should be enough to allow you to turn it. If not, try holding the jar or blender upside down and letting the water seep under the lid. If the jar or blender lid is stuck because someone screwed it on the wrong way, this will help loosen the threads.
Technology to the Rescue
It's a rare lid that won't come off after being treated with hot water, but when it happens, you may need to reach for a tool. Tapping the lid or the jar won't help because there's no vapor lock to break, and putting the jar in the freezer, which is an oft-cited remedy, takes too long and may not work anyway.
The tool that you need is a pipe wrench because of its wide jaws. Depending on the size of the lid, you may also be able to do the job with locking pliers. If the lid is very small – for example, a copper bottle cap is stuck – you may even be able to do the job with conventional pliers.
Some lids are too wide even for a pipe wrench. To get one of these off, you might need a strap wrench, which is a tool plumbers use to loosen and tighten large pipes. If you don't have one, get a strong friend instead. After both putting on rubber gloves, one person grips the jar with two hands, the other grips the lid and you use your combined strength to achieve your goal.