 Kill ' Em All features intricate riffing reminiscent of the NWOBHM bands played at high velocity . The album is considered crucial in the thrash metal genesis because it introduced fast percussion , low @-@ register chords , and shredding leads to the genre . Hammett played some pentatonic patterns in addition to his breakneck solos . Ulrich adopted a double time snare pattern that would become a mainstay on Metallica 's subsequent albums . Hetfield 's vocals evolved from the melodic wail on No Life ' til Leather to a rough @-@ edged bark and the entire band played faster and more accurately on Kill ' Em All . Music writer Joel McIver said Burton 's and Hetfield 's performances were nearly virtuosic , because of the smooth @-@ sounding bass of the former and the precise picking skills of the latter . According to journalist Chuck Eddy , the juvenile lyrical approach to topics such as warfare , violence and life on the road gives the album a " naive charm " . The musical approach on Kill ' Em All was in contrast to the glam metal bands who dominated the charts in the early Eighties . Because of its rebellious nature and Metallica 's street appearance , it appealed to fans who were not into the mainstream of hard rock . 
