how do you differ between these two genre descriptions?

Speed Metal is Heavy Metal played faster whereas Thrash Metal is different in terms of riffs, vocal style and intensity. I'd cite Chosen Ones by Megadeth as a Speed Metal song for example.

That's just my 2 cents on the subject though.

A lot of people describe Speed Metal as a cross between Power and Thrash. Other people use Speed Metal as a cross term rather than a genre.

Frankly, this debate has been going for years and there has never been a conclusion drawn up. I never bother using the term "Speed Metal". When describing banks like Metal Church, Iron Angel and Exciter, I stick with "Power Thrash".

To me, speed metal is just power metal. But faster.

So it doesn't really get to be its own genre IMO.

I differentiate between the 2 with the drum beats. Thrash will more often be off-beat, whereas speed is just standard rock drumming sped up.

I also use it as a crossover term, but as its own genre, i.e. the Euro speed/power metal scene.

Speed Metal to me is the early European power-metal stuff... Running Wild, Helloween, Rage e.t.c...

I think speed metal is thrash metal that has retained its heavy metal roots. While still being heavy and crushing it is also melodic and intricate and of course, fast.

I would call bands like Artillery, Coroner and other Euro bands speed metal as they have taken elements of American thrash, Euro metal and UK old school to create Speed metal.

I dunno, i've always thought as speedmetal to maintain the same intensity as thrash but just not as raw and heavy, which its why its hard to define metal church's genre. a lot of old german bands like heavens gate, rage and mind odyssey were all a mixed genre of power / speed metal but its easy to distinguish between thrash and speed metal, eg. kreator = thrash where as iron angel is blatent speed metal.

Speed Metal is more akin to Heavy Metal, whereas Thrash Metal takes lots of cues from Punk. Early Blind Guardian, Running Wild, Exciter, Grave Digger, Rage, etc., are Speed Metal, and Dark Angel, Sadus, Sabbat, Destruction, Nuclear Assault, etc., are Thrash. Of course, there's plenty of grey areas, and this is just one man's definition. In fact, there are people who contest that what we commonly refer to as Thrash is actually Speed, and Crossover bands such as DRI are Thrash.

yeah Thrash probably varies more...whereas speed is...speedy?

anyone who listens to / has heard Meshuggah...speed or thrash? Its off-beats, but im not sure.

Meshuggah are neither

Meshuggah's first album, Contradictions Collapse, is quite thrashy.

good point James...and i guess they don't really fall into anything.

and the biggest reason early Meshuggah was so thrashy was because they started out trying to pretty much copy Metallica's early stuff.

I've always been one of those people who say,@what's the bloody difference',but in the last year I've been researching the subject and realised that I was a bit ignorant about the thing.
But most of the desciptions mentionened by you guys are pretty much there.I've kinda come up with my own conclusion.The genre was catagorised by the major rock press back then as Speed and Thrash metal.
The big bands would be described as covering both territories.But the way I describe speed metal is fast with a simple hook line throughout the song,and thrash metal with more of a pushed to the limit crushing vibe created in a more extreme way.
I still find it fairly complicated to explain.But when I hear a song with a simple and tight picking hookline at a blistering tempo throughout the song,I always think'speed metal'.

I expect non thrash bands that are realy heavy like Pantera probably called a song like Fucking Hostile as speed metal.

METAL DAVE,WEYMOUTH.

Speed Metal sounds boring. Thrash Metal sound sexy.