Top Ten Lesser Known Metal Albums That Are Very Influential

The Top Ten
1 Possessed - Seven Churches

First Death Metal album ever.

2 Slayer - Hell Awaits

This priceless jewel of raw brutality must be the first record that defines how the thrash must be: aggressive and relentless!
With Sacrifice Torment in Fire, Kreator Flag of Hate, HellHammer and the like

3 Venom - Welcome to Hell
4 Godflesh - Streetcleaner
5 In Rock - Deep Purple
6 Exhorder - Slaughter of the Vatican
7 Body Count - Body Count
8 Venom - Black Metal
9 Celtic Frost - Into the Pandemonium
10 Judas Priest - Stained Class
The Contenders
11 Rising - Rainbow
12 Melvins - Melvins
13 Dark Angel - Darkness Descends
14 Sin After Sin - Judas Priest
15 Keeper of the Seven Keys, Pt. 2 - Helloween

I agree it was very influential but Blind Guardian and Iced Earth were not influenced by this album. Hansi Kursch stated it many times (besides, I really don't hear Kiske's era stuff in Blind Guardian and Iced Earth).
Only Blind Guardian's first 2 albums (with speed metal) were partly influenced by Helloween but it was another Helloween album - Walls Of Jericho.

It was enormously influential in power and melodic metal

16 Fear Factory - Soul of a New Machine
17 Neurosis - Souls at Zero
18 Wake Up and Smell the Fish - The Jungle Medics
19 Sepultura - Morbid Visions
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