What is the difference with metal and rock??

ROCK MUSIC::
Rock music is a form of popular music with a prominent vocal melody accompanied by guitar, drums, and bass. Many styles of rock music also use keyboard instruments such as organ, piano, or synthesizers. Rock music usually has a strong back beat, and often revolves around guitar, either electric or acoustic.

Rock music has its roots in 1950s-era rock and roll and rockabilly. In the late 1960s, rock music was blended with folk music to create folk rock, blues to create blues rock and with jazz, to create jazz-rock fusion, and without a time signature to create psychedelic rock. In the 1970s, rock incorporated influences from soul, funk, and latin music. Also in the 1970s, rock developed a number of subgenres, such as soft rock, heavy metal, hard rock, progressive rock, and punk rock. Rock subgenres from the 1980s included synth-rock, hardcore punk and alternative rock. In the 1990s, rock subgenres included grunge-style rock, britpop, indie rock, piano rock, and nu metal.



METAL MUSIC:
Heavy metal (sometimes referred to simply as metal) is a genre of rock music that developed in the late 1960s and early 1970s. With roots in blues-rock and psychedelic rock, the bands that created heavy metal developed a thick, heavy, guitar-and-drums-centered sound, characterized by highly amplified distortion and fast guitar solos. The All Music Guide states that "of all rock & roll's myriad forms, heavy metal is the most extreme in terms of volume, machismo, and theatricality."

Heavy metal has long had a worldwide following of fans known as "metalheads" or "headbangers". Although early heavy metal bands such as Led Zeppelin, Black Sabbath, and Deep Purple attracted large audiences, they were often critically reviled at the time, a status common throughout the history of the genre. In the mid-1970s, Judas Priest helped spur the genre's evolution by discarding much of its blues influence; the New Wave of British Heavy Metal followed in a similar vein, fusing the music with a punk rock sensibility and an increasing emphasis on speed.

Heavy metal became broadly popular during the 1980s, when many now-widespread subgenres first evolved. Variations more aggressive and extreme than metal music of the past were mostly restricted to an underground audience; others, including glam metal and, to a lesser extent, thrash metal went on to mainstream commercial success. In recent years, styles such as nu metal have further expanded the definition of the genre.