Metallica have enjoyed a long standing association with the hometown San Francisco Giants and it continued over to this year with the team welcoming the band for the fourth annual "Metallica Night." But this year came with one feature that other years didn't. Baseball legend Willie Mays was in attendance, celebrating his 85th birthday, and Metallica's James Hetfield serenaded "the Say Hey kid" with a rendition of "Happy Birthday" as the audience joined in.

Hetfield sang from the top of the dugout, while bassist Robert Trujillo held up a Willie Mays sign. As the camera panned upward to Mays in one of the luxury boxes, Mays looked down with a smile and jiggled his ear with a chuckle. Watch it all play out here.

The evening also found Hetfield and Kirk Hammett doing their annual rocked up performance of the National Anthem just before the game and drummer Lars Ulrich threw out the first pitch, then signed the ball for pitcher Jason Law. Guitarist Kirk Hammett also took part in an interview during the game. "I idolized Willie Mays when I was in 4th and 5th grade just like all my friends did," stated the guitarist. Watch his full interview here.

Even though the game is complete, there is a current auction that wraps today where fans can bid upon the orange Giants guitars played by James Hetfield and Kirk Hammett during the National Anthem, Metallica signed San Francisco Giants jerseys, signed bats and baseballs, signed Metallica photos, as well as bats and balls signed by a number of major league players. Proceeds from the auction will benefit the Surfrider Foundation, the Giants Community Foundation and Amnesty International.

As you may remember, earlier this week Metallica took to the beach with Giants pitcher Jeff Samardzija to pick up trash as part of a Surfrider event leading up to "Metallica Night."

Check out additional photos posted by the band below and Metallica's own photo gallery at this location.

Watch Metallica Perform the National Anthem at the San Francisco Giants Game

See Where Metallica's Albums Landed on the Top 80 Hard Rock + Metal Albums of the 1980s

Metallica, Kill 'Em All Deluxe Box Set: Unboxing With Narration