Extended solution

Because the spiral is placed closely above the flame, it can withdraw a lot of energy from it. The metal from the spiral is an excellent heat conductor. Therefore it can draw enough energy from the candle so that the wax cannot burn. This energy is transported from the spiral towards your hand - the spiral gets warmer. Once the spiral is pulled away from the candle, enough energy can reach the candle in order to burn the wax. Therefore, the form of the spiral is not important. However, it is very useful because a lot of metal is put in a very small space. Therefore, it has excellent characteristics to conduct energy from the candle towards your hand.