Metallica's "Motorbeath" off their Kill 'Em All debut is a breakneck classic that helped define the thrash genre. Energetic with a slight New Wave of British Heavy Metal bend, the song has never failed to sound inspired and fresh even 33 years later. After three decades of existing as a neck-wrecker, James Hetfield has put a new and softer spin on the track.

The Metallica frontman took the stage to perform an acoustic rendition of "Motorbreath" at the Acoustic-4-A-Cure benefit show in San Francisco, Calif. last night (May 15). The typically gritty singer took a new approach, showcasing his higher and cleaner singing, reaching an apex before the three minute mark where he lets his voice soar with narrow vibrato.

Hetfield is joined onstage by another musician — mostly out of frame — who plays along on a lute, providing additional vocals, harmonizing with Hetfield and giving the Metallica classic a new life. Most interesting is the gentle picking approach the frontman utilizes, slowing the overall tempo and truly transforming the music. The performance didn't stop there as Hetfield also tackled another Metallica classic "The Unforgiven" and covered Screamin' Jay Hawkins' "I Put a Spell on You."

In addition to Hetfield, other notable rockers took the stage at the Acoustic-4-A-Cure benefit, including Tommy Lee, Joe Satriani, John Mayer, Melissa Etheridge and Train‘s Pat Monahan. Hetfield's daughter Cali even joined him onstage at one point. Funds from the benefit show were donated to the Pediatric Cancer Program at UCSF Benioff Children’s Hospital.

Metallica have been involved with their San Francisco community quite a bit this year. The band recently celebrated the fourth annual 'Metallica Day' at the San Francisco Giants' baseball stadium, Robert Trujillo and Kirk Hammett teamed up on a local beach cleanup and the band made a return to their 1980s Bay Area home where they received a proclamation from the mayor.

See Where James Hetfield Ranks Among the Top 50 Hard Rock + Metal Frontmen of All Time

10 Unforgettable James Hetfield Moments

More From Loudwire