Best Musical Scales for Metal

Darkest scale in music to be honest. It's the same as harmonic minor but with the #4 of Lydian. So, on the root, you can build either a diminished triad, a minor triad, or a minor #5 triad, which is also an inversion of the major triad you can build on the 6th degree. You can hear this scale at the start of Save Me by Avenged Sevenfold. Also, it's the 4th mode of Byzantine/Double Harmonic Major.

The two octatonic (8 note) scales built off alternating whole and half steps. You can build so many types of chord progressions you can't build with diatonic scales in these. If you play minor chords instead of diminished chords, you can compose some nice Danny Elfman-esque things. You don't even need to play any diminished chords or major chords. Every degree in the scales can form a diminished triad, and all a diminished chord is is a minor chord with a flattened fifth. All the fifth interval does is reinforce the root, so who says you have to play the flat five?

Ionian/Natural Major with a b2 and a b6. Its modes are Lydian #2 #6, Ultraphrygian, Hungarian Minor/Double Harmonic Minor/Gypsy Minor, the Oriental scale, Ionian #2 #5, and one of my favorites, Locrian bb3 bb7. I can't include all of these on the list because it would be repetitive, but they're all amazing sounding scales.

EVIL. Aeolian with a b2 and a b5. Second mode of Aeolian/Natural Minor and seventh mode of Ionian/natural major.

Not too dissonant or too major sounding. Fifth mode of the natural minor scale. Just Aeolian with a b2.

These are the first scales every guitarist should learn, not the damn pentatonic scales. They should be taught the natural minor/Aeolian and natural major/Ionian scales first and then the pentatonic scales as an extension of that, and how they fit into minor and major contexts.
I put them both into the same entry so I could avoid repetition. Also, Ionian/natural major is the 3rd mode of Aeolian and Aeolian is the 6th mode of Ionian. Also, shout-out to Dorian and Lydian for all my fellow Dream Theater fans.
And to those of you who say Ionian can't be metal, listen to some Iron Maiden. And some pre-Painkiller Judas Priest.

Phrygian with a natural 3. The tonic chord is a dominant chord. 5th mode of Harmonic Minor.

Aeolian/Natural Minor with a natural 7 degree. It's literally just every Yngwie Malmsteen song ever.

My favorite pentatonic scale. The intervals you're working with are the root, a b2, a 4th, a 5th, and a b6. It has a very exotic *Japanese* flavor to it and it works best over minor chords. The stuff I write isn't really heavy on major chords, although major chords pop up plenty, so I love playing this scale. You can hear it in Home by Dream Theater, along with the aforementioned Aeolian, Phrygian Dominant, Phrygian and Harmonic Minor scales.