Metallica blows balls.
These days anyway...
Take Ride The Lightning, Master Of Puppets, and of course And Justice For All... a few tracks from The Black Album if I'm feeling generous (which I am today, say thanks), and you have a cohesive block of listenable metal/hard rock material. The rest is, assuredly trash. Some of it might be symphony-backed trash, but it is trash.
Kill 'em All is thrash trash. Due to the production (or lack thereof, depending on how you look at it) one can't even make out Cliff Burton's awesome bass awesomeness, which is really the only point of Metallica anyway...
Testement is right! Big ups on that. But also Megadeth, Iced Earth, Kreator, motherfucking Overkill, Sodom, Metal Church... well fuck I have had this discussion too many times in my life to carry out listing all the metal and thrash bands that are better than Metallica ever was... but if anyone gives a shit, prompt me...