This one's going to get me into a little bit of trouble, but I don't think this album is anywhere near the greatest metal album of all time like most people seem to think.
Hell, it isn't even close to Metallica's best album (That being ...And Justice for All, even with it's complete lack of bass).
Overall, it's a solid album. But the quality is a tad spotty for me.
It starts off very strong with Battery and Master of Puppets. Two absolutely fantastic songs. The Thing That Should Not Be is a decent track, but repetitive and let down big time by Lars' drumming (Which honestly lets basically every album of Metallica's down, so not really unique to Master of Puppets, but there's just so much sloppy and frustratingly simple drumming on this album. For once I want Lars to be able to come up with a fill that's more interesting than just walking the toms or a basic single stroke roll, and to play with feeling instead of just holding the drumsticks with a deathgrip).
It's frustrating because Lars' drumming makes up a huge aspect of Metallica and their sound. It's legitimately iconic, and they probably would not have been anywhere as big had he not been behind the kit making the music accessible. But I honestly feel like basically any other metal drummer could have done a better job and made every Metallica album better.
Anyways, I'll try not to bitch about Lars as much going forward but god is it difficult when drums are generally the thing I pay attention to the most when listening to music (Particularly metal, a genre that is replete with drummers who could vie for the crown of greatest drummer ever).
Onto the next song, Welcome Home (Sanitarium), which is another fantastic cut from the record. Great musicianship all around. I will say, when Metallica got past ...And Justice for All, I really felt like Kirk Hammet got extremely formulaic and repetitive with his guitar playing, but here it's just generally great, inspired riffs and playing all around. And Welcome Home/Disposable Heroes are great examples of that.
Not to mention, having Cliff Burton's bass playing to play off of helps a lot. Just great basswork here. Disposable Heroes, despite my praise of it though, I do have some small quibbles with, particularly with some of the odd phrasing from Hetfield, along with some of the cleaner rhythm guitar going on feeling a little at odds with the heavier riffs from Hammet.
Leper Messiah is probably the weakest track on the list barring The Thing That Should Not Be, and the biggest reason is again Lars, so many stilted little breakdowns and bad fills. There's some good in here, particularly when it speeds up and Hammet and Burton are allowed to really get heavy.
Orion is a fantastic instrumental. Not much else to say there, although would have liked a little more distortion on the rhythm guitar earlier in the song. and finally Damage Inc. is better than I remember, with one of the better performances from Lars on the album, honestly.
So yeah. I know I was far more negative on this album than my rating will suggest, because it really is a great album. Just in the grand scheme of Metallica's discography, thrash metal, and metal in generally, I honestly think this is one of the most overrated albums of all time. I do think my previous listen to this years ago is coloring my opinion of this album a bit, but I did enjoy it more this time around.
TL;DR: Great album. Wildly overrated. Lars' drumming is horrifically bad.