If your toolbox has a lock similar to a file cabinet, you might be able to use the next technique- Look for a thin metal tool that can fit into the keyhole of the toolbox. The tool should be inserted all the way to the lock's back. Turn the tool like a key while jiggling it up and down.
A Toolbox can be opened by a locksmith by using special tools. Locksmiths can also offer you replacement keys for your toolbox. But, if your lock is broken then the best option is rekeying.
The lock code for your box can be found in a few different ways. The lock code will be imprinted on one side of the box's keys if you still have them. The external lock cylinder where the key is inserted is the other option.
If you are thinking about drilling a lock then keep this thing in mind the locking plug will be destroyed but it will keep the mechanism in working order. It is not suggested to do it but still, if you have to do it then it is suggested to examine the lock and complete the task properly by using the right tools for the job.