When your power tool doesnt respond, you need to check three things:
If there is no weird sound or smell coming out of your tool then there is a solid chance that the motor is fine and the trouble lies somewhere else.
Switch is normally found right behind the primary trigger and is responsible for controlling the electric current from the socket to the tool. A new switch will mostly work all the time but as it gradually wears off you will have to pull the trigger two or three times to make it work. As the switch gets older, you will find yourself pulling the trigger several times and finally it will stop working completely.
When the trigger fails to turn your power tool on, it means the switch is broken and needs a replacement. Remember when the problem is with the switch, machine wont stop working on its own until you leave the trigger.
If there is no problem in powering on your tool but it stops working during the work then the problem lies with carbon brushes. These brushes are responsible for transferring the power to the electric motor of your tool and are important part of it. When carbon brushes start to wear off, the power transfer to the motor is cut down so the machine stops working. Sometimes, tapping and slapping creates the contact so the tool starts working again but thats not a permanent and reliable solution.
If you are using Metabo power drill then you can shop for Metabo replacement parts on different online stores including carbon brushes. Carbon brushes also indicate that there may be a problem with your electric motor. If your power tool stops working during the project then you might want to take a look at your motor as it may be worn out. However, in most cases your power tool starts working again when you replace the worn out carbon brushes with the new ones.