Why do Catholics use candles at Mass?
Even though candles no longer have a practical purpose, the Church still requires their use in the liturgy.
With the exception of the Easter Vigil and the Advent Rorate Masses, in modern celebrations of the Mass, candles typically do not retain their former practical purpose of illuminating a darkened space. Yet, the General Instruction of the Roman Missal (GIRM) states, “The candles, which are required at every liturgical service out of reverence and on account of the festiveness of the celebration, are to be appropriately placed either on or around the altar.”