Beatallica has been an underground favorite for years. They combine Metallica and Beatles songs into a metal-pop mashup. Beatallica's members have pseudonyms that combine names from both bands, such as Jaymz Lennfield, Grg Hammettson, Kliff McBurtney and Ringo Larz.
Sgt. Hetfield's Motorbreath Pub Band is a fun album with titles like "Blackened in the U.S.S.R." and "A Garage Dayz Nite." The way Beatallica blends the sounds of Metallica and The Beatles actually takes a fair amount of skill, and they do it really well. Lennfield's voice sounds a lot like Metallica's James Hetfield, and the band members are equally adept at '60s psychedelic pop and more intense metal.
The Beatles and Metallica are two of the most popular and influential bands in music history, and obviously Beatallica's mashups don't reach the levels of the originals, nor are they meant to. It's just a fun and well done homage to a couple of great bands.
