What does chanting mantras do?

Although we are spiritual in essence, we have a material body, with material senses which we use to enjoy the various pleasures of this world. This covers our true identity and we forget that we are actually spiritual in essence. By regularly chanting sacred mantras you can gradually clear away this covering and the result is gradually increasing peace, happiness, satisfaction, and love for the Supreme Soul and others. You are a spiritual person so you need spiritual activities to make you happy and satisfied. Nothing else in this world can do this.