What should I do if my key doesn't open the lock?

The key is bent：
For example, if you use the key to cut something, such as using it as a box cutter or can opener, this may cause the key to bend. If the key is bent, it may get stuck in the lock when you try to enter your home. If this happens, you need to straighten the key as much as possible.
You can do this by tapping the key with a hammer on a smooth, hard surface. You don't want to flatten the key, so be careful to remove only the curved portion of the key. This may be much easier if you have a bench. You can place a piece of wood between the hammer's keys to protect it. The video below shows you how to straighten a key using a vise and a wooden stick.

Can't insert the key：
When the key cannot be fully inserted into the keyhole, there may be an obstruction. The pins may become corroded, or the pin chamber may become worn. Always do your research before trying to fix key and lock problems on your own, as mistakes can result in damage to the lock or door. In some cases, it's to call a locksmith to fix this specific problem.
If you want to try to fix this problem yourself, you can try using graphite powder or graphite spray. Coat the key with graphite and insert it into the keyhole. The graphite will act as a lubricant, helping to unlock the brake bolts that may become clogged with debris over time.

The key broke in the lock：
When you try to enter your home and a key damages the lock, it can be difficult to retrieve the damaged key. You can use the tips of needle-nose pliers to remove the damaged key and pull it out of the keyhole.
However, it is important not to use force as this could damage your lock or even your door. One of the worst mistakes you can make is trying to put the key back together with super glue. Glue residue can damage your keys and locking mechanism. The video below demonstrates nine different ways to remove a damaged key from a lock.