If heavy-metal fans are supposed to be such hardcore loyalists, what is it about a few haircuts, some eyeliner and a little songcraft that throws ’em into such a dither? Load — Metallica’s very long (78 minutes and 59 seconds on the nose) goodbye to the moldy stricture and dead-end Puritanism of no-frills thrash — is easily the heaviest record of the year, a seething beast of meaty, focused guitar dynamics, taut art-pop drama, unexpected vocal-harmony kicks and intensely personal lyric aggression. You’ve got to be dead from the neck up and the waist down not to swing with the tangled riffing and blastoff choruses in “Ain’t My Bitch” and “King Nothing.” Singer, guitarist and attitude captain James Hetfield has, with the advent of middle age, exchanged his original cannonades of adolescent distemper and CNN-inspired vitriol for more intimate disclosures of anger, loss and retribution. But he’s done so with undiminished venom, proud authority and even the occasional self-deprecating giggle. As Hetfield snorts at one point against the black-lava ooze of his and Kirk Hammett’s guitars, “Oh, it’s too good to be/That all this misery/Is just for oh, poor, twisted me.” Get over your Master of Puppets fixation, and twist with this.