Grunge fusing with thrash metal? Neat! (We would get "thrash-grunge")

Thrash takes classic metal and speeds it up and adds much more technical guitar work. Grunge metal (Alice in Chains) slows classic metal down and tunes everything down by an octave.
So if you combine them don't you just get down tuned classic metal?

Nah.

I'd imagine a song with grunge's angst lyrics (for the most of time) like social alienation, self-doubt, abuse, neglect, betrayal, social and emotional isolation, a desire for freedom, etc., but can also bottow themes from thrash metal like nihilism, injustice, death, suicide, etc.

Often, I'd think there would be a tempo change between grunge's sludgy slow speed and thrash metal's fast adrenaline-fueled speed, although it is entirely possible to make a 'thrash-grunge' song with more emphasis on one's speed than the other and make countless variations of it.

Sonic Youth's free-form noise, dirty, fuzzy, downtuned guitar tone, dissonant harmonies and prominent alternative rock influence from grunge would be mixed with thrash metal's faster and technical features. It wouldn't be uncommon to hear a simple bluesy guitar solo, then a second solo more reminiscent of thrash.

Basically, "start sloppy, end with technicality" or "start with technicality, end sloppy".

That would be a hell of an album.

IKR?
I'd listen to that.

So basically Godsmack with a faster tempo. They’re heavy and got the groove of grunge

I'd imagine a song with grunge's angst lyrics (for the most of time) like social alienation, self-doubt, abuse, neglect, betrayal, social and emotional isolation, a desire for freedom, etc., but can also bottow themes from thrash metal like nihilism, injustice, death, suicide, etc.

Often, I'd think there would be a tempo change between grunge's sludgy slow speed and thrash metal's fast adrenaline-fueled speed, although it is entirely possible to make a 'thrash-grunge' song with more emphasis on one's speed than the other and make countless variations of it.

Sonic Youth's free-form noise, dirty, fuzzy, downtuned guitar tone, dissonant harmonies and prominent alternative rock influence from grunge would be mixed with thrash metal's faster and technical features. It wouldn't be uncommon to hear a simple bluesy guitar solo, then a second solo more reminiscent of thrash.

Bass, for the most part, would be dirty and fuzzy, like the guitars.

So I imagine some lyrics of a machine head song with the same tempo but the tone of nirvana. That would be cool

Or some lyrics of a Metallica song at first with Nirvana's tempo and tone and some Alice In Chains-style riffs, but then evolved to a song, while still keep Nirvana's tone, it gradually changed to Metallica's own speed and riffs.

Hmmm I could attempt to do this idk when but it’s definitely possible

Nice.

Btw, might kinda be easy to turn 'St. Anger' into thrash grunge mixed song.

That’s true