Hey there buddy! Love seeing a new student here!
And I also LOVE the fact that you're asking about metronome practice, because it's a big thing. I'll try to answer this as best as I can, as someone who once played the Nightmare solo and had to practice it to a metronome.
Feel.
Let me say that again.
Feel.
And louder for the people in the back.
FEEL.
What I mean by this, is that if you have a slowdowner tool like The Amazing Slow Downer, you listen diligently to each section at a time and when it's slowed down, you can pat your leg or tap your foot along with the drum beat so you can get a sense of FEEL for the RHYTHMIC notations of the solo. For example, I think it's like the 4th or 5th measure of the solo, that there's 16th notes that then go into a triplet feel. Hear that section as many times as you can, play along with the music, and while you're playing it, HEAR the beat in your head to internalize it, so that you can understand how it's played against a BEAT and not against MUSIC. I hope that makes sense.
Then once you get it down with the music, take it over to the metronome and try it there. Most people don't understand how important it is to truly FEEL rhythmic notations of lead parts, so that you CAN play it against a metronome.
It takes a lot of conscious effort to LISTEN to yourself playing and say "Hey, that doesn't sound quite right. Let me try that again." Being self aware is massively vital.
If you don't understand what I mean, or if you have further questions, PLEASE be transparent and I'll be more than happy to make a video for you!
Cheers brother!