Ok guys, I have a few questions regarding thrash metal, so here they go:

1)What scales and techniqes are used when playing thrash?

2)Is there a general lyrical theme, or is it just the instrumetal part that classifies thrash?

3)Do you think you could implement death growls with thrash riffing, or do you think it would sound like shit?
You can do what you want.
Trash metal uses any scale you want. There is no such thing as a "thrash metal scale".

There are no limits. Do you want sounds right to you. Try everything.
lots of thrash bands (early 80s) used growling and today a few newer bands use em too.

a lot of earlier thrash bands stuck to pentatonic scales but that doesnt mean you cant use whatever you want.

there is no definite lyrical theme to thrash, but a lot of people think there is, which is why a lot of newer thrash bands sound ridiculous when they talk about killing posers and moshing
Just do whatever you want. Don't limit your creativity to a certain genre. You will use stuff of the music you listen to anyway, so: Don't bother about genres.
1. Scales? Doesn't really matter, techniques? Maybe you should listen/learn some thrash metal and find out.

2. Lyrical theme? Whatever you want

3. Death growls? Why not experiment and see what you think sounds good.
I agree. If you stick to what's typical of thrash it may limit you to exactly that.

However, thrash techniques used include chugging/triplets on the low E, use of double stops, pedal tones, palm muting

Scales used by bands like Slayer include Natural Minor, Phrygian, Phrygian Dominant and Harmonic minor etc, but if you mix it up chromatically you'll get some interesting sounds as long as you don't sound like you're just modulating constantly.

With regard to vocals, you could mix in some death metal growls but generally thrash uses a "pushed" vocal style - not necessarily screaming but not necessarily clean vocals. Chuck Billy from Testament used that style in their early albums and still does live, but now he mixes in some death growls, since their album Low and still on their last record The Formation of Damnation.

Hope this helps!

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Thanks alot Sleazeball, that really helped alot. And also thanks to everyone else for your comments. I'll be sure not to limit myself, I was just asking for some broad scales and techinques which could be used for writing/playing thrash metal. Next time I play, I'll be sure and just REALLY LISTEN and see what I think...
And again, props to sleazeball for his in depth answer ::
As DiminishedFifth says:

^^The above is a Cryptic Metaphor^^

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