What happens if there is too much voltage?

it truly depends on the device that is supplied and what you mean by " too much". Generally overvotage is bad and will shorten the components life, considering it was desined and built to work in a certain range. Severe over voltage will cause almost all electronic devices will burn though very quickly. A motor windings will burn out in short order or the insulation will punch through and cause a turn to turn short. Purely resistive load will over heat and fail very quickly