How to learn metal singing? (roars and growls)?

Ok im a girl and iv never done this before but a friend of mine would like me to at least try to learn a metal song by this band called straight line stitch. Iv never done this before and im very nervous. Is their any exercises that would help me achieve the metal voice tone or if their a special technique i should know? anyone who does this could you please give me some pointers. Please don't leave hate comments i don't have time for your 'opinion' on music.