MEGADETH; "Youthanasia" (Capitol Records). * * 1/2

"Youthanasia" is not Megadeth at its best (for that, look to "Rust in Peace"), but the new album is definitely the band's most sophisticated release to date.

With the success of "Countdown to Extinction," band leader/

guitarist Dave Mustaine and his baby went commercial. It was almost inevitable for the band, whose music became accessible thanks to movies like "Last Action Hero" and Beavis and Butthead's compilation album, "The Beavis and Butthead Experience."

(Mustaine also came close to damaging the band's image by appearing on "The Late Show with David Letterman" awhile back.)

"Youthanasia" is more mellow than, say, "Peace Sells, But Who's Buying?" and "My Business Is Killing . . . and Business Is Good." But it does offer driving rhythms ("Reckoning Day," "Elysian Fields" and "The Killing Road") and some excellent lyrics (the hit "Train of Consequences" and "Victory," which is actually the band's history in a jewel case).

Mustaine's cynical lisp and anger rage on, but the double-speed drums and orchestral arrangements are held to a minimum.

TESTAMENT; "Low" (Atlantic). * * 1/2

This is guitarist James Murphy's break-in album. While the man is not former guitar-virtuoso Alex Skolnick, he's pretty darn good.

After losing Skolnick to Savatage, Testament comes back with a hard-hitting album designed to knock the socks off any listener. The album is consistent, and Testament's style hasn't changed much since it's second album, "The New Order."

That's where the problem lies: This new album sounds like a rehash of its predecessors.

While the band's lyrics have matured over time, the sound hasn't. From the heavy brooding of the title cut to the mellow ballad of Native American disenfranchisement ("Trail of Tears") to the instrumental "Outro" of "Last Call," the album could be a clone of "Practice What You Preach" and "Legacy."

Headbangers will flip around with this new release, and fans will praise the band for the new lyrics.

Still ,it must be remembered Skolnick left because he wanted to branch out with experimental metal. Testament should have listened to him.

QUIET RIOT; "Down to the Bone" (Kamikaze Records). *

One of the melodic metal bands from the 1980s MTV days tried three times to duplicate the success of 1981's "Metal Health" but to no avail. So, why does it keep coming back to haunt us?

The band the late, great Randy Rhodes (who performed with Ozzy Osbourne) started has become somewhat of a parody of itself. Now, that doesn't mean the band is talentless. But guitarist Carlos Cavazo can do much better than the old Slade rehashes "Cum on Feel the Noize" and "Mama We're All Crazee Now." Both of which were virtual note for note duplicates of the originals without any real creative hooks.

"Down to the Bone" is better than that - but that's not really saying much.

Eddie Van Halen's pioneering pull-off licks (other bands use them so much they've become "rip-off" licks) are redundantly redone on this album. No excitement here - and that's a shame.

Speaking of Van Halen rip-offs, Quiet Riot even manages to remake a famous Kinks song - no, not "You Really Got Me" or "Where Have All the Good Times Gone" - but "All Day and All of the Night." A warm, screeching guitar solo anticlimaticly leads into this cliche-ridden piece. It would have been cool in 1978 or 1983, but now it feeds the "duh, dude" mentality (stereotype?).

The album's major problem is the timing. When other metal bands were picking out the neo-country rock blues, Quiet Riot held back. Now the album's title cut tries to tap into that tired sound.

Then, trying to capitalize on the melodic metal of earlier hits, Quiet Riot rips itself off with "Twisted" and "Hell or High Water."

Avoid this one.

SPUDMONSTERS; "Stop the Madness" (Massacre Records). * * 1/2

What should you expect from a band whose album cover depicts post-nuclear holocaust mutants toting around the heads of Mick Jagger, Jon Bon Jovi, Vince Neil (the former Motley Crue vocalist) and W. Axl Rose? In this case, hard-core, thrash-metal punk.

Beavis and Butt-head might refer to this band and Gwar's little brothers, but Spudmonsters is a band with potential. The album, though a bit repetitive, bursts with energy and brings to mind midcareer Anthrax injected with a little Slayer.

Each of the 17 songs, which average about three minutes, hooks the listener and doesn't let up. As confrontational as the lyrics might be, the antagonistic tone is filled with tongue-in-cheek humor - topics range from taking out the garbage ("Garbage Day") to credit collectors ("Repo Man," which carries sound bytes from the Emilio Estevez cult favorite of the same name).

This clever but somewhat monotonous album carries mosh-easy cuts and will, undoubtedly, turn a few heads (and break a few necks). But one must remember, the band is in its beginning stages and has time to mature.

Let's just hope the campiness remains.

RATINGS: four stars (* * * * ), excellent; three stars (* * * ), good; two stars (* * ), fair; one star (* ), poor, with 1/2 representing a higher, intermediate grade.