When you think of the pioneers of metal the first band you should think of is Black Sabbath but right behind them is Deep Purple. More on the iconic band in a bit.
First the trip from Deep Purple to Dio is a very direct one as Ritchie Blackmore and Ronnie James Dio were both in Rainbow together.
Now with other bands I have been picking somewhat obscure songs to play but with Deep Purple there is only one song that I can pick, That of course is ‘Smoke on the Water’. In my generation when you first picked up a guitar the first riff you learned to play was the opening Riff to Smoke on the Water, even before you learned to play the Iron Man riff from Black Sabbath.