I love me some Dio, but Mob Rules and Heaven and Hell, just don't do it for me.
Whereas stick some Holy Diver on, and 30 odd years just fade away... \m/
Trying to reply but I'm unable to paste text or links 😤
Take a look at the Wikipedia page for legato then look at the guitar section ☺
Or go to the YouTube and search for 'legato guitar' 🎸
If speed = shredding then there's no difference if you use a technique based on legarto.
Funnily enough if I shred on guitar, I have to pick each note. But on bass I'm a fingers player and can use legarto.