Oh man. So many.
@rajillustration Judging by your list, I'm going to go with these bands/acts:
Ben Folds / Ben Folds Five
Lady Lamb
Dear in the Headlights
Steel Train
Bleachers
The Format
Mason Jennings
Carl Perkins in Dearland
George Harrison
The Regrettes
PHOX
Peter Gabriel
Genesis
I hope you dig them.
Have you ever listened to Elliott Smith? He's very essential for right now, especially if you like dark, existential lyrics. Very similar to the Beatles with a voice that sounds like rainwater flowing down a rusty pipe.
I suggest you start with See You in Heaven or Waltz #1
I also recommend Grizzly Bear. Their lyrics are atmospheric and the music is chilling. Plus the lead singer has an awesome voice and he doesn't use machines at all to amplify his sound. Everything you hear is real.
I recommend you start with Two Weeks or Speak In Rounds
Florence + the Machine
She’s just so emotional and amazing. She has a good bit of music out and I feel like her tone changes per album 
My main deep dives are basically Underoath and The Devil Wears Prada. They're those bands who scream all nasty into the mics with the emo singing. Plenty of albums for the (relatively) short time they've been around. 7 albums for both, with other songs in between.
Part of why I listened to them was that I was Christian and looking for some dope music to vibe with that you'd never hear in church. I've long since grown out of that mentality, but their songs have stuck with me lol the other undeniably more important part is that they shaped a lot of my musical tastes early on and even influenced my growth as a musician and songwriter so yea
Shoutout to Metallica, they're cool too (except for the Lulu album collab bc yikes). I generally like a lot of what they do, but for me, everything is easily overshadowed by what I think is their best work, the S&M live performance with the San Francisco Symphony~
@DanielRKM Oh at one point I was like deeeep into Ben Folds but then I kind of stopped listening to them because they reminded me of an ex boyfriend and just forgot about them. Time to regain that part of my life from that break up eons ago.
@WhiskeyClone Oh! Grizzle Bear! I think I heard a few of their things. I remember liking it.
@ar-ninetysix oh yeah I heard Metallica did a thing with the SF Symphony and I just have never listened to it. This is a good reminder to go back.
@mlocik97 never heard of BigRoom so I'll have to check that out.
@kmlangley uf love Florence. I've only listened to like one album though. So good rec!
@VibrantFox oh I don't know if I've heard of Lain Volta or if I just don't remember them--I'll have to check that!
@cherrystark yes the 80's were a great time for rock.
My current deep dives have been the Beatles, Coldplay, and Elton John. I forgot how much I enjoyed their music so it's been nice 'rediscovering' it.
Other deep dives I've done since quarantine started have included Lorn, Queen, Lady Gaga, and M83. I definitely recommend M83 and Lorn. They're both very inspiring to me!
King Crimson would be a really fun deep dive, especially if you start going into the individual member's past projects. Adrian Belew particularly...
His social page is here
https://twitter.com/LainVolta
but the music he's most known for (under she music) can be found here or his youtube
and then there's a bunch of demos he has on soundcloud that give glimpses into the development of some of his bigger songs or ones that just weren't fully released at all
Honestly, I just rely on the figure skaters to supply music in my life. A lot of it is repetitive, for obvious reasons, but they do go for weird stuff sometimes.
I listened to a lot of Hip-hop 
Whenever it is a singer I listened to the ones in the 80's-90's, Rnb
The Miseducation of Lauryn Hill
This one is my deep dive Any song/Album from Sa-Roc ( idk if ya might like her though 
)
Nitty Scott?? : The Art Of Chill
I chose these people because there the only ones I listened to a full album of that are females.
Here's a sampling from my some of my playlists. I think we have similar tastes.
From my female artists playlist:
Cherry Glazer "Told You I'd Be with the Guys" "Distressor" "Isolation"
LUNA AURA "Honey" "Enlgish Boys"
Amy Winehouse --Back to Black album was one of two CDs in my car at all times.
Bridge City Sinners "St. James Infirmary" "Witches' Wrath"
Dakota Staton "Cry Me a River" <-- this is my favorite song.
Deap Vally "Baby I Call Hell"
Estrons "I'm Not Your Girl"
Gin Wigmore "Black Sheep" "Man Like That"
Grace Mitchell "RIIICH"
Hayley Williams "Simmer" Sudden Desire"
HOLYCHILD "Plastered Smile"
Ida Maria "I Eat Boys Like You For Breakfast"
Katy Perry "I Kissed A Girl -Live AT MTV Unplugged, New York, NY/2009" (a jazz version, and the most superior version)
The Kills "Sour CHerry" "No Wow"
Kim Petras "There Will Be Blood"
LPX "New Mood"
Madd "British Racing Green"
Meg Myers "Desire" Jealous Sea"
Paloma Faith "Upside Down" "Only Love Can Hurt Like This" "Trouble with My Baby"
Rina Sawayama "Comme Des Garcons (Like The Boys)"
VUKOVI "C.L.A.U.D.I.A." "Colour Me in"
Willa "Swan"
WRENN "Craigslist Personals"
YONAKA "Bad Company" "Punch Bag" "Teach Me to Fight"
Hayley Kiyoko "Demons"
From other playlists:
Arctic Monkeys AM -album.
ASIAN KUNG-FU GENERATION "Re:Re: (Single Ver.)
BABYMETAL "Gimme Chocolate" "Awadama Fever"
Black Lips "Modern Art" "Bad Kids"
Blood Red Shoes "I Wish I Was Someone Better" "ADHD" "It's Getting Boring by the Sea"
cleopatrick "hometown"
Caleb Hyles "Again" <--guy does amazing covers of pop.culture songs.
Death From Above 1979 -- honestly, any things from them.
Depeche Mode "Enjoy the Silence"
The Killers "Humans" "All These Things That I've Done" Also, Sam's Town.
My Chemical Romance.
Punch Brothers "Julep" "Another New World"
Rage Against the Machine
Remo Drive "Yer Killin' Me"
Sincere Engineer "Corn Dog Sonnet No. 7"
The White Stripes
The xx "Islands" "Crystalised"
I have loads more. Just give me a genre or feel.
Have fun!
We all know that my suggestion will probably be too much.
But since you said you like Metallica...
I suggest
Anthrax
Overkill
(Overkill has 19 studio albums! 19! And each one has a distinctly different flavor while still retaining what makes them...Overkill.)
Proposition 1: George Clinton
Because:
- a lot to go through (funkadelic, parliament, all stars, his own stuff...)
- a definite cult following and a whole music scene developed around his work
- different styles from your usual playlist so it can bring in some new inspirations and fresh ideas
- brainy at time yet groovy so won’t disturb your working vibe
Second proposition:
Einsturzende Neubauten
Because:
- again a lot to go through
- closer to your previous list so maybe a safer bet
- a very interesting and clear evolution over the year, always between raw and refined
- again, the right mix between brainy and melodic to create a working atmosphere which is inspiring but not overtaking
Persona games OST by Shoji Meguro. They are really versatile, they are really pleasant, they are great to listen to when you need to concentrate on the drawing or to feel free and careless and like you're having summer vacation in school. There are just enough beats in them, giving you just the right amount of wish to tap your toe or sing along.
Blind Guardian. Amazing metal, amazing nerd references. Of course you want to listen how Feanor fucked up everything in Hansi's voice!
Jeremy Soule. Well, this guy is not metal, nor does he sing, but his tracks are something I am literally listening for hours on a damn repeat, they are too good. He made music for Neverwinter nights, Harry Potter, Elder scrolls, etc., etc. Perfect background music, nothing else to say.
Susumu Hirasawa. Okay, Hirasawa is not for everyone, but he is basically the only techno musician I listen to, because his music sounds special, just perfectly balanced techno. Hirasawa's songs are really powerful, each in it's own manner. He can do crazy, he can do battle, he can do a tear-jerker.
Mine would be Bix Biederbeck, 1920's jazz and also DJango Reinhart and Stephan Grappelli Le Jazz hot.
I love all kinds of music, from The HU to Oneus and Lay to Dorothy and Ivy Levan but a lot of times I like to go way back in time to the 1920's and see what's there. Oh, and every now and then a little Portuguese Fado.
I think my best such experience was Opeth, and I'll suggest it to anyone who can tolerate a bit of ... mild extreme metal (makes no sense said like that).
I was 'harassed' by friends for years to listen to it because 'it's something for you Vothn' but I was a classical music person at this time 
But that meant that when I finally listened, they had a huge discography already. I listened to everything on a couple of days. One of my best music experiences.
