Input (grade 13): Alt-metal bands commonly emerged from hardcore punk (Corrosion of Conformity), post-hardcore\/noise rock (Helmet, The Jesus Lizard), grunge (Alice in Chains, Soundgarden), or industrial (Ministry, Nine Inch Nails).
Output (grade 9): Popular alternative metal bands are Alice in Chains, Nine Inch Nails, System of a Down, and Korn.