Metal is a genre of music which has been around since the 70's and has become
one of the most popular genres of music in modern day society. With the second british invasion of bands like Judas Priest and Iron Maiden, metal was quickly accepted into the American underground. Metal is a very hard genre to define due to the various opinions of many people. Some may say GnR was metal and so it started with bands like that, others may say the Metallica started it all.
Whatever you say you have to give credit to Metallica for making it big with metal and making it a more known genre. Whether or not they sold out once they got there, that's not for me to say. Today metal is a global movement and has hundreds of sub-genres that delve deeper into harshness, speed and brutality, but it is safe to say that metal gave them their roots and remains
the greatest genre ever.