Short circuit USB port with multimeter
As mentioned in the video, the outer metallic, rectangular casing is connected to the ground. So inserting the thick lead of the multi meter to touch the positive supply will cause the lead to short the positive supply and the outer casing which is ground.
The thin metal pin is used only to ensure a gap between the pin and the outer casing while it is touching the positive supply. It is is not a mistake proof method. If that pin leans too much, it can still short the supply and the ground. The pin may not limit the current.