Im pretty old school and came into music in the 80's. My tastes mostly reflect that
I like a lot of bands, but there are standouts.
Well-known:
Iron Maiden - First real metal band I liked.
Metallica - I remember hearing the solo from Master of Puppets the first time and was blown away that you could make those noises with a guitar
Megadeth - The anti-Metallica, but I loved both. Maybe Megadeth just a little more. Rust In Peace best album.
Testament - Just really like the heaviness of it.
Queensryche - Didn't become popular until the 90's with the release of Empire. Everything up through Promised Land. Later stuff not so much.
Less Well known or known only in certain cirlcles:
King Diamond\Merciful Fate - love macabre, dark and theatrical aspects and the guitars are phenomenal
Dream Theater - Most progressive metal band I know
Pagan's Mind - Norwegian prog metal. Haven't released anything in a while and might not ever again, but everything they've done is great.
Symphony X - More prog metal. Michael Romeo is also a god\mythical creature on guitar.
Pantera - Just fast heavy musical aggression. Love it. "Dimebag" Darryl Abbott (RIP) was awesome.
Virtuosity:
Steve Vai - I'm an atheist, but he's as close to the existence of god as one could be I think
Yngwie Malmsteen - Neo-classical shredding master
Joe Satriani - up through The Time Machine and some on later albums; Vai's guitar teacher
Certainly not exhaustive. I love 80's hair metal and thrash