Master of Puppets has been my starting point and while listening to Kill 'Em All I have noticed something very sorrowful that has lead to me not listening to Master of Puppets all that much.
Metal, thrash Metal, it don't matter. It is ultimately rock music. The trouble with Metallica is that they decided along the way, while improving on composition and lyrics, to change the sound of their guitars into these big, lifeless, machine-like instruments with no soul. A guitar needs to wail. The guitars don't wail on Master of Puppets. They sound like machines. But on Kill 'Em All, the guitars sound pretty damn awesome. Which results in me enjoying the album more despite not being as good as Master of Puppets (For one, James Hetfield doesn't sound as good there as he does on Master of Puppets). But the guitars, man. It seems to me that the sound of the freakin' guitars is pretty important.
Example: Seek & Destroy versus The Thing That Should Not Be. I mean what the fuck is going on with the latter song? The guitars sound fucking stupid. Real talk. It sounds too damn heavy and obnoxious. Guitars need to sound like guitars, like they do on Seek & Destroy. Fortunately for the song Master of Puppets, it's not so bad, but for the rest of the tracks on the eponymous album the songs are not so well off.
Really really real talk.