Metallica began reissuing remastered versions of albums in various formats in 2016. The band released its 1983 debut Kill 'Em All and 1984's Ride The Lightning, and logically that means the next one to be reissued is 1986's classic behemoth of an album, Master Of Puppets.
According to Lars Ulrich in an interview with Voir, the remaster should be out later this year, or at least soon right after the start of 2018.
It should be coming maybe later… We'll try to see if we can get it out at the end of this year. It's coming soon. We're working on it. There's a lot of stuff associated with Master Of Puppets; that's a big project. And we've spent so much time looking forward, with Hardwired and so on, but Master Of Puppets is obviously next. [It will be out] hopefully late this year. If not, soon thereafter.
Yes, Master Of Puppets in all its remastered glory is going to be amazing, but the real thing to look forward to is what comes next. The followup to Master Of Puppets is the very bass-less 1988 album …And Justice For All, which hopefully will get remastered in 2018 and have some justice done to Jason Newsted's playing.