Looking for Melodic Thrash Metal or Melodic Deaththrash.

'Melodic' is a pretty big generalization, considering many thrash metal bands have melodic passages and soloing (Testament and Forbidden, for instance) but they aren't considered 'melodic' bands. I also have NEVER heard any melodic death/thrash bands. Not denying their existence, I just don't know about it.

I think Hexen fits your rigid description though. You may want to check into Annihilator (songs like Imperiled Eyes and Alice In Hell) if you've never heard of them, aswell.

OP is probably referring to stuff like The Crown, Exmortus, etc. You know, bands influenced by SOTS-era At The Gates.

Testament and (early) Annihilator are good calls on the more melodic side of thrash. Also check out Xentrix if you like Testament. You can also cross over to speed metal influenced thrash with stuff like Heathen and the likes of them.

try ruinside ?

Artillery, Arsenal from Costa Rica, for melodic death thrash maybe later Arghoslent or Ares Kingdom

Check out Blo.Torch.
http://www.metal-archives.com/bands/Blo.Torch/10421
http://www.youtube.com/watch?v=ZzZdFaL_CFw
I have their self-titled album only but it's pretty much what you're looking for - melodeath with a thrash backbone.

Other prominent bands that come to mind are Bloodshot Dawn, Darkane and Battlecross

I don't know if that's exactly what you're looking for but you can try,for instance,The Haunted,Hatesphere and At the Gates (maybe the last one is too obvious).
By the way,have you tried with Kreator's last albums? they have some things that are kind of melodic.

LOL yes At the Gates it's too obvious. I was really just wondering If there was such a thing as straight up melodic thrash (should have worded my post better). Phantom Antichrist was one of my favorite albums of 2012

I'll second Hexen, one of my favorite bands. Also check out Obliveon and Defiance.

Megadeth with Rust in Peace era is generally considered melodic thrash. A lot of the bay area thrash bands tend to be soemwhat melodic, and more so than their German-counterparts. I would expect melodic thrash to be used as another term for bands with a lot of groove, often melodic death metal elements.

I tend to think of it more like thrash bands that aren't as hard hitting in terms of drumming and that use more harmonized guitars. Testament on their early albums for instance, as opposed to Low or The Gathering.

Speaking of which, Defiance is a fine choice. I personally love Beyond Recognition with its almost progressive flair. It's a pretty cool album indeed.

Heard of Sylosis? http://www.youtube.com/watch?v=q_qf_fc7GDY

Check out Essence http://www.youtube.com/watch?v=2tSRP0lbqHM

/me looks at bassist.

/me declines the offer.

What's wrong with the bassist? He just has glasses.

Anyways, I don't think it's been mentioned (sorry if it has), but perhaps some Arsis would fit your description. They're melodic-thrashy-tech death. Check out A Celebration of Guilt. I just heard Unwelcome today. It was decent, but more tech-death than thrash though.

Stone are the greatest

Sanctity: http://www.youtube.com/watch?v=P6ySMEZwpJA

I, too, feel that Hexen can be defined as melodic thrash. Also give Decadence a try. The other bands have already been mentioned I believe. I would also give Dr. Living Dead a go

Here's a sample of Decadence : https://www.youtube.com/watch?v=Ap9NkedTXKA

Oh, yeah, almost forgot. Definitely check out Skeletonwitch.

Check the thread date.