Master Of Puppets

Meaning

Meaning varies by interpreter.  Most commanly accepted meaning is heroin addiction.
Stephen:  "Knuckles had no lyrics at one point and Tails had planned an acoustic interlude, but other than that we had nothing.  I was fooling around with some really fast riffs and Knux came in.  He insisted that because he was just thinking about Puppets that those riffs had to be in there, it was like fate or something like that.  So we put 'em in there."
Kevin:  "I wanted something dark that would scare the shit outta everyone again.  I kinda thought Lightning was just a little too nice.  So I came up with these lyrics.  Originally about heroin, I changed it just enough to keep the listener guessing and headbanging."

Live

After it's release, it is a steady part of the live show; with the acoustic interlude often replaced by low, clean-toned electric.
Kevin:  "I just love how this song came out, but after Stephen died, and I took over the axe, sometimes I feared it because that intro, as cool as it is, is a BITCH to play at that speed.  But I do it anyway.  And the audience just loves to scream 'MASTER' at the top of their lungs."