What is the function of the spring inside a spark plug

[Minsid]

If the electrode can move, what keeps combustion gasses from moving up the center of the ceramic?
Spring stronger than compressed gasses?
Knots

Probably. Napkin math with 200psi acting on a 1/8" dia electrode only generates 3 pounds.

 

[workinonit]

The spring is a bi-metallic element that lights up the inside cavity of the spark plug when it is energized so the current knows where to go and doesn't bump into things.

I win! But some of the answers were really close competition. Obviously, very few people know anything about spark plugs..

 

[zzvyb6]

Spring is an inductor. When couple with a resistor, its a filter to smooth out the spark supply spike to produce a pulse.