Rock and Metal music are currently being played and developed in a number of countries and in a number of different languages, but it still originates from the Anglo-American world (United Kingdom and USA specifically). What historical events and national characteristics about he UK and the US led to the development of these music genres in the US and the UK and not in other countries with a long and rich history of music and culture, such as France and Germany.
The origins of Rock are almost entirely American, and come from the influence of Blues into mainstream music, which comes almost entirely from African American musical influences due to the slave trade. I wrote a post about this in how it relates to Jazz and the progression from African slave work chants to early Blues and Jazz:
But nearly all of the early Rock genre is a derivation from the Blues. Hell, a lot of the early white Rock artists (Elvis, Jerry Lee Lewis and others) just wholesale ripped off blues songs from black artists. A good example of this is Hound Dog. Everyone attributes it to Elvis, but it's a hardcore blues song by Big Mama Thornton: https://www.youtube.com/watch?v=ZrieOEPJCos
Elvis just sped it up and whitewashed it.
Even the Rolling Stones were stealing and repurposing Blues into the 60s and 70s, and got sued for it.
As for the UK, they just followed to lead of the US. They would have had the advantage of speaking the language, and didn't have the segregation laws of the US, so a lot of black artists would have travelled there. But yeah, Rock is the Blues, and the Blues are African American.