During the 1970s and 1980s, there was a cultural phenomenon known as the Satanic Panic. It involved the general public believing that Satanic cults were active across America and doing harm. According to those who believed in this conspiracy, heavy metal was a dangerous genre that had the purpose of spreading Satanism.
In hindsight, it is somewhat understandable why so many tabloids such as the Mirror were concerned about the influence heavy metal had on young listeners. The earliest bands of this genre would often use supernatural imagery. However, this was generally for shock 
value and to give out an edgy image.
Most mainstream heavy metal bands did not support Satanism. They were simply utilising horror as a theme that would appeal to a wide range of listeners. Contemporary studies found that the rumours of widespread Satanic cults were unfounded. They were merely an urban legend believed by people susceptible to moral panics.
Today heavy metal continues to be enjoyed by people all over the world. Meanwhile, the conspiracy that it encouraged Satanism has decreased in believability. Sociologists have analysed this urban legend and found it shows the dangers of not verifying facts.