Candles primarily serve the purpose of providing rituals, and spells with power. They primarily do this because they emit power while burning, and this action can be harnessed in order to power your workings. This not only works with candles, and works with anything that burns such as a bonfire or torch. Things that are near to the flame or are burning up in the flame give that power to the candle. This fire interaction gives off a lot of energy, and is very easy to give intention to and because of that it has become a staple in many spells. There are substitutes to using candles in your practice but a lot of them don’t give off as much power but can be useful when you are not able to use fire.