The letter M is represented by the International Phonetic Alphabet symbol /m/. It is a voiced consonant and does not have voiceless counterpart.

You will find the /m/ sound in words such as:
mother /ˈmʌðər/
trumpet /ˈtrʌmpət/
home /hoʊm/

/m/ is an bilabial sound. Bilabial sounds are sounds that are produced using your two lips. To produce this sound, your lips will be pressed together as air flows out of your nose.