Hey there,
I and from Germany and always looking for better metal pedals. I have had cheap products and some more expensive like the Rat or Boss MT-2 but couldn’t resist to post my opinion here.

Pro:
Sound:
The EHX Metal Muffs sound was the best I have ever experienced. It gives you the ‘chunky’ sound with lots of distortion but still remains very clear (even through cheap amps), so you can hear every different note. You would expect this only from highly priced amps.

Style: Many nice slogans inside the packaging and even inside the pedal itself. I like these kinds of ‘easter eggs’.

Contra:
Durability.
It’s produced sloppy like it was made by children in China. Seriously, my Pedal was used as all my others were, no scratches, only a bit of dust AND IT BROKE IN MY LIVING ROOM IN 4 DAYS!! THIS MUST NOT HAPPEN WITH PEDALS BEYOND $20. Its now only making some fuzz mixed with the guitar singal, not even the bypass is working anymore. I have had BOSS pedals falling from heights above 3 foot without any damage.
I read that the Metal Muff’s 9V jack breaks really often, so I connected a battery but mine seems just ‘overall broken’. I’m studying some kind of engineering stuff, so I will probably try to repair it in a few years. Until then I can really say that this cheap production will not pay off, although I will have to buy another one, as soon as my hatred against EHX is gone and I have gathered another 80€. The next is gonna have a guarantee, for sure.

Its kinda my only guitar thing that ever broke, I would never take one of these on stage, as I’m the lucky owner of a good used metal amp made in Germany that will not break.