Why does every mantra start with OM?

According to the Vedas, the word ''OM'' itself is so powerful that if a person does chant this word regularly, he can accumulate lots of positive energy around him and the surrounding around him becomes more positive. With the daily chanting of OM, all miseries and sufferings of a person will be gone forever, your every desire gets fulfilled and you find contentment in life.

It is said that no mantra and puja is considered to be completed without using the word 'OM'. According to the Vedas, the whole universe couldn't be form without the utterance of OM and the word Om always echoes and emerges from the entire universe.

Om is composed of three letters a, u and m, in which a means growth and u means progress and the last word m means meditation. OM is used before the pronunciation of every mantra because it is believed that no mantra utterance is complete without using it.