Oh, and Helm: Iron Maiden, At the Gates, Kreator, Kataklysm, Dark Tranquility, Hypocrisy Callenish Circle, Kalmah, Bolt Thrower, DISMEMBER
That's a good mix of the old and the new, all metal too. What about Dismember? Like an Ever-flowing Stream is one of the best swedish death metal albums of all time. SKIN HER FUCKIN' ALIVE and all. I personally find Kataklysm waaay too clicky for my tastes and I stopped listening to Dark Tranquility by Enter Suicidal Angels or aboutso, dunno how ridiculous they might have become today.
Be careful with too much of the burly death metal, it's pretty monochromatic really. For Heavy Metal to give you all it can you need juxtaposition from the harsh to the weird, and from the weird to the soothing (yes, such Heavy Metal exists) so on. Don't become a blastbeat fiend.
Dragonforce
Bubblegum bullshit. They look like a metal band. They play like a metal band. But they're soulless. Sadly such is the path of almost all latter-period power metal. The old stuff deserves your attention, though. More below.
Are there any bands that the mighty Helm imposes upon me?
Let's see.
Fates Warning, Heir Apparent, Diamond Head, Omen, Manilla Road, Cirith Ungol, Sanctuary, Slauter Xstroyes, Brocas Helm, early Angra, Lord Weird Slough Feg, Savage Grace, Heathen, Attacker, The Hammers of Misfortune, Andramelch (ITA, NOT the death metal Adramelech), Liege Lord, Crimson Glory, Savatage, early Nevermore (up to Politics of Ecstasy), Lordian Guard, Maudlin of the Well, Warlord, Cloven Hoof, Virgin Steele, The Vision Bleak, Helloween, Syris, Vicious Rumours, Agent Steel, Judas Priest (up to Painkiller of course), Jag Panzer, Queensryche, Symphony X, Rainbow and of course, the Black Sabbath.
All this has a soul, no monkeys aping the form or anything of the type. These are HEAVY METAL. Now, moving on:
Doom Metal (including doomdeath):
Candlemass, Memory Garden, Trouble, Pentagram, St. Vitus, Thergothon, Esoteric, dISEMBOWELMENT, Shape of Despair, early My Dying Bride, Unholy, Forsaken, The 3rd and the Mortal, While Heaven Wept, Abstract Algebra, early Anathema, early Paradise Lost, Orphaned Land, Asunder, The Gault, Morgion, early Cathedral (up to and including Forest of Equillibrium), Doomsword, Evoken, Skepticism, Veni Domine, Dusk, Krux, Saturnus, Winter, Worship
Thrash and technothrash:
Dark Angel, Sieges Even, Sepultura, Anthrax, Destruction,
Watchtower, Exodus, Deathrow, Megace, Forbidden, Depressive Age, Flaming Anger, Calhoun Conquer, Mekong Delta, Thought Industry, Cyclone Temple, Annihilator, Believer, Artillery, Forced Entry, The Haunted (first album), Civil Defiance, Aftermath, Coroner, Assorted Heap, Invocator, Kinetic Dissent, Municipal Waste, Paradox, Sacred Reich, Sore Plexus, Stone, Testament, Windham Hell
Progressive Metal:
Psychotic Waltz, Fates Warning (later), Aghora, Sieges Even (later), Watchtower (later), Coroner (later), Atrox, Behold... The Arctopus, Blind Idiot God, Conception, Frantic Bleep, Garden Wall, Gordian Knot, Cynic (later), Kayo Dot, Confessor, Loincloth, OSI, Saviour Machine, Shadow Gallery, Spastic Ink, Spiral Architect, Thought Industry (later), Verse and Radiation, Voivod
Death Metal:
Death, Autopsy,
Demilich, Demigod, Torchure, Suffocation, Gorguts, Atrocity (early, for heaven's sake!) Asphyx, Kaamos, Grave, Dismember, Ripping Corpse, Dim Mak, Cynic, Atheist, Monstrosity, Incantation, Immolation, Malevolent Creation, The Chasm, Acid Bath, Human Remains, Crimson Massacre, Crypt of Kerberos, Disharmonic Orchestra, Edge of Sanity, Godflesh, Macabre, Martyr, Negativa, Mithras, Morgoth, Necrophagist, Nocturnus, Obituary, SUP, Tiamat
Black Metal:
Mercyful Fate, Celtic Frost, Hellhammer, Bathory, Arcturus, Immortal, Averse Sefira, Blut Aus Nord, Taake,
In the Woods..., Ulver, Weakling, Burzum (handle with care), Absu, Elend, Empyrium, Enslaved, Fleurety, Gehenna, Keep of Kalessin, Melechesh, Negative Plane, Rotting Christ (very early, demos and up to first album, PERHAPS), Dissection, Sacramentum, Samael, Sigh, Solefald, Ved Buens Ende
That's enough to keep you occupied to track down for a while. one band per genre is in bold. Start there. Even if that's all you check out from my list, you'll become a better person for it.