Speaking of....have you heard Theodore Zirgas?!!
!!!!
Insanity!!!!
He has a video where he plays 16ths at 300 bpm!
I did a post here awhile ago called how fast the 'fastest' are playing and I put it at around 220 bpm +/- 10 bpm ((fastest player before Zirgas I'd heard was Francesco Ferari, and he's usually rocking at 230 bpm))
Well fuggedaboutit!
300 bpm is 20 nps. Phew!
Yet, they asked how he got to be so f*cking fast and he just said "I practiced with a metronome, making sure to get everything perfectly."
On the other hand, Yngwie Malmsteen CLAIMS to have never done anything like that. He says he just played all the time, to music, and if he couldn't play something, he didn't play it until he could. I'm not sure how much of that I believe---but if it's true, it means that both approaches CAN work!
Oh, and that's a good thought---coordinating your right and left hand with each click of the metronome. There are metronomes that click out different note durations for you, and maybe that would help?
Back In Black isn't a song. It's a divine call that gets channeled through five righteous dudes every thousand years or so. That's why dragons and sea monsters don't exist anymore.