The joke should have grown stale by nowband mashes up Beatles favorites with Metallica lyrics and thrash-metal attitudebut somehow Milwaukee’s Beatallica keeps finding ways to keep it fresh. The group’s latest album, Sgt. Hetfield’s Motorbreath Pub Band, contains songs like “Blackened the U.S.S.R.,” “Hey Dude,” and an “Enter Sandman”/“Taxman” sendup called simply “Sandman.” Expect to hear plenty of mutilated classics tonight when the band plays an 8:30 p.m. show at Vnuk’s.