Not sure I follow this... The ignition key makes a low-current contact that is connected to the starter solenoid via a relatively small wire (18 AWG?). This signal is what causes the plunger (solenoid) to move into the high-current contacts which carry the battery current directly to the starter motor. The solenoid (plunger) itself does not carry battery current, it is the head of the plunger which makes the connection between the two contacts. The arcing that occurs each time this happens is what pits the starter contacts as well as the head of the plunger.
The head of the plunger is actually insulated from the plunger shaft itself:
An "enhancement" I have seen is to remove the starter control lead from the key assembly and install a starter button on the dash. Just turn the key to 'ON', hit the momentary pushbutton on the dash and viola! A Ferrari!