There is a big debate on shredding these days... Many of my younger students refer to shredding as guitar soloing/ad libbing - not just playing fast. I have always loved to play fast, but interspersed with melodic lines in the same way the great jazz legends have done. Listen to Allan Holdsworth... a highly revered jazz guitarist.. overdrive/distortion, some of the fastest playing on the planet, but what tone and musicality! Not metal, but has inspired many metal players. When guitarists get together... these genres (metal, thrash, blues, rock... whatever...) fall away. My Turkish student is into the harsher end of thrash metal... but we were doing air guitar the other night, trading riffs, listening to AC/DC, the Doors, the Who, Foo Fighters, White Stripes, you name it... the range was huge.. and loving it! And we were both watching each other's fingers on Back in Black to see who got it RIGHT!
And I still think Coltrane shredded that sax like no-one!