Here's my picks for each subgenre: 

Heavy: Sabbath and Maiden's first 5 albums each; Judas priest's Sad wings of destiny, Screaming for vengeance, and painkiller

Death: scream bloody gore, altars of madness, none so vile, the bleeding, severed survival, onward to golgotha

Melodeath: the jester race, the gallery, slaughter of the soul, storm of the light's bane, heartwork

Black: transylvanian hunger, pure holocaust, in the nightside eclipse, de mysteriis dom sathanas, under the sign of the black mark, vikingligr veldi

Atmospheric/ambient black: Hvis lyset tar oss, filosofem, bergtatt, 

Prog: images and words, Metropolis part 2, Blackwater park, crack the skye, from mars to sirius, lateralus

thrash: master of puppets, ride the lightning, peace sells but who's buying, rust in peace, reign in blood, mental vortex

Stoner/sludge: dopethrone, take as needed for pain, when the kite string pops, houdini, leviathan

Akercocke - Words That Go Unspoken, Deeds That Go Undone.  

Progressive Death Metal done right.  Very catchy and brutal.  

The Phantom Agony- Epica

Widows Weeds- Tristania

THERES SO MANY but im a thrash fan so for me its

Rust In Peace - Megadeth

The Ultra-Violence - Death Angel 

Among The Living - Anthrax

Ride The Lightning - Metallica

i have many more but heres some albums for now

Sonic excess in it's purest form- Crowbar.

I've grown obsessed w this album but sludge might not be for everyone 🤷

Gore Obsessed, the wretched spawn and Tomb mutilated!! 

1184 by windir

none so vile by cryptopsy, amZing albm

If you're into more melodic stuff, I'd recommend The cold white light, Frozen, The funeral album - Sentenced, Fallen - For my pain..., A virgin and a whore - Eternal tears of sorrow. 

hmmm one of my FAV bands is dystopia theyre pretty popular but i always recommend them theyre like thrash metal i think

Tarot album by aether realm

Boy do I have some suggestions for you! I'll try to list stuff that hasn't been posted yet.

Annihilator - Alice In Hell (Thrash Metal)

Broca's Helm - Defender Of The Crown (Heavy Metal)

Buckethead - Monsters and Robots (Electronic Metal)

Faith No More - The Real Thing (Funk Metal)

Faith No More - King For A Day Fool For A Lifetime (Alternative Metal)

GWAR - This Toilet Earth (Thrash Metal)

Mercyful Fate - Melissa (Black Metal)

Mercyful Fate - Time (Heavy Metal)

Mr. Bungle - Mr. Bungle (Avant-Garde Funk Metal)

Mr. Bungle - Disco Volante (Avant-Garde Sludge Metal)

Mr. Bungle - California (Avant-Garde... Art Metal?)

Mr. Bungle - The Raging Wrath Of The Easter Bunny (Thrash Metal)

Slipknot - Mate. Feed. Kill. Repeat (Death Metal)

Thanatopsis - Thanatopsis (Jazz Fusion Metal)

spit - kittie

oracle - kittie

LD 50 - Mudvayne

Toxicity - System of a down

Kosherat- Grand Belial's Key.

Really anything from them is pure gold, and that includes Arghoslent! 

but for Black metal in the more "Mainstream" sense for sure Emperor's debut album and Immortal's debut as well. 

Viktoria by Marduk is one o my personal faves.

Got Some - Snot

IOWA - Slipknot

Show no Mercy - Slayer

Through Silver in Blood - Neurosis

When the Kite String Pops - Acid Bath

Cause of Death - Obituary

Obscura - Gorguts

The Fragile - Nine Inch Nails

scream bloody gore is a must death metal album, 10/10 would recommend

The Sound of Perseverance by Death.

these are some my favs!!

ride the lightning- metallica

rust in peace- megadeth

number of the beast- iron maiden

holy diver- dio

issues and self titled- korn

american psycho- misfits

GALNERYUS's The Flag of Punishment. It's a MUST-LISTEN! Maybe it's just me, but it can be difficult to find Japanese Metal with 80's Heavy/Prog Metal vibe to it. Other than that, I could only think of X JAPAN's Blue Blood.

listen to curntan n wall

Chaosphere by Meshugga is possibly their best album 

Split Image by Excel

South of heaven by slayer

South of heaven by slayer

Pain remains - Lorna shore

The battle of Yaldabaoth - Infant Annihilator

Warlocks Grim & Withered Hags - Hellripper (Black/Speedmetal)

Keppers of the Seven Keys Part 1 - Helloween (Powermetal)

Hidden History of the Human Race - Blood Incantation (Deathmetal)

Tapping the Vein - Sodom (Thrashmetal)

Alice In Hell - Annihilator 

(most underrated band and lead guitarist btw)

nothing more - spirits.

nothing more - self titled. :)

try all of the dethalbums and gore 2.0 !! just skip over a doomstar requiems soundtrack bc its better when u watch it :3

I'd have to throw in one very underrated album and go with Dehumanizer by Black Sabbath. 

it's basically they're Painkiller, released in 92, and is one the bands heavest albums, and was a reunion of the Mob Rules album

the bleeding

ball spouter by alienation mental is some really good expiremental brutal death metal/deathgrind album

Cryptopsy's None So Vile is the greatest death metal album of all time. absolute must listen

Here's a couple albums where after I heard them for the first time I just had to stop and process what happened. So I think everyone else should hear these masterpieces

I Let It In And It Took Everything - Loathe

This Bright And Beautiful World - Greyhaven

Burying Brightness - Boundaries

A Tear In The Fabric Of Life - Knocked Loose

I Hope We Make It Out Of This Alive - Sold Soul

Old Souls - Make Them Suffer

Dear Lemon House, You Ruined Me - Kaonashi

It Lingers - Fromjoy

The Dark Pool - Thornhill

The Way It Ends - Currents

The Sea Of Tragic Beasts - Fit For An Autopsy

The Color Clear - Reflections

Color Decay - The Devil Wears Prada

Slipknot - Mate Feed Kill Repeat 

welcome to Horrorwood: The Silver Scream 2 -Ice Nine Kills

a lovely mix of metal and theater. they take horror movies and make them into music. highly recomend.

Black Breath-Sentenced To Life

Operation Mindcrime - Queensryche

one of the best albums out there fr

some thrash metal underrated songs:

suicide - Hirax 

voivod - Voivod

the denist - Messiah

tormentor - Slayer

neurotica - Ironchrist

Arntor by Windir 

Dragged into sunlight - hatred for mankind

Its a 10/10 

Fredrik Thordendal- Special Defects

Testament- New Order

James Murphy- Convergance

any pantera album

Got a couple for ya: 

Interceptor - tales of mayhem

Tank - filth hounds of hades 

Dub buk - idu na vy!

First one is 1st wave black metal (think of first venom albums)

Second one is nwobhm

And the third one is pagan bm 

Oh definitely Cowboys from Hell and Vulgar Display of Power by Pantera,Rust in Peace by Megadeth,Black Metal by Venom(who are often regarded as pioneers of thrash and black metal),Human,Symbolic,Sound of Perseverance by Death(although i highly recommend listenin to their entire discography).Storm of the Light's Bane by Dissection is one of my favorite for agessss

meteora - linkin park 

adrenaline- deftones

kill em all - metallica 

system of a down - system of a down

toxicology- system of a down

trauma - i prevail 

true power - i prevail

Hearken the End - Hulder