Sonic Booms : Check List ****<i> Great Balls of Fire</i> ***<i> Good Vibrations</i> **<i> Maybe Baby</i> *<i> Running on Empty </i>

**MEGADETH. “so far, so good . . . so what!”. Capitol. **METALLICA. “Kill ‘Em All.” Elektra. Something old, something new, both likely to blow the socks off of you. The old (a reissue of Metallica’s 1983 debut LP) and the new (Megadeth’s hot-off-the-presses third effort) represent two leading speed-metal forces, and a mix-and-match jumble of personnel shifts.

Metallica’s 4-year-old “Kill ‘Em All” features bass playing by the late Cliff Burton, and songwriting by Dave Mustaine. Mustaine left Metallica in ’83 to form Megadeth, whose latest recording marks the arrival in the band of drummer Chuck Behler and guitarist Jeff Young.

Got that straight?

Regardless of the vintage of these sonic booms, or which musicians did what, this is raw, furious, bone-crunching stuff. It’s for people who like their metal really heavy. Wimps need not apply.

“Kill ‘Em All” is the longer of the two records, but it may also be the lesser one. Except for two songs from last year’s “Garage Days Re-Revisited” sessions that have been tacked on to the album, the music here was recorded nearly five years ago, and Metallica’s writing and playing skills have grown tremendously in the meantime.

Back then, songwriters James Hetfield and Lars Ulrich and, in some cases, Mustaine didn’t have a whole lot to say--but did have a frantic, pulverizing way of saying it. “Kill” traffics in highly aggressive, often militaristic phrases and images, while a few songs are self-conscious observations about the cause-and-effect of thrash metal. Some are both, like “Metal Militia,” a metal anthem couched in military terms.

This is a promising, if limited and erratic collection--but it’s essential for fans of speed-metal and Metallica, because we know now they fulfilled that promise.

Megadeth is just hitting its stride with “so far.” That’s clear from the opening “Into the Lungs of Hell,” a torrid instrumental featuring the first of many you-take-the-high-notes-I’ll-take-the-low-notes guitar duels.

This thundering, molten metal rarely lets up. Interestingly, where Megadeth is most reined in--comparatively speaking--is on a version of the Sex Pistols’ “Anarchy in the U.K.,” featuring ex-Pistol guitarist Steve Jones. Mostly, though, the quartet pursues its own purposeful anarchy, flying through intricate arrangements and multiple tempo changes, stitching together a crazy-quilt of metal riffs and rhythms.

Megadeth’s lyrics are more concerned with humans and issues, from loneliness and isolation (“In My Darkest Hour”) to drunk driving (“502”). But, really, speed-metal is far less about words than music, and either of these records could probably break a lease--and maybe an eardrum.