PAT BOONE is more than in a metal mood – he‘s gone to pot!

The squeaky-clean ’50s crooner is singing the praises of marijuana, saying it’s helped his 36-year-old grandson cope with a debilitating injury.

While strongly opposed to “getting high,” the 78-year-old conservative Christian is making an exception for legal use for Ryan, son of Lindy Michaelis, one of Pat’s four daughters.

“Pat feels as long as it’s not being used for recreational purposes, and is used to help people cope with pain and anxiety, then it’s all right,” revealed a family friend.

A dozen years ago, Ryan was severely injured in a three-story fall through a skylight while sunbathing on the roof of his apartment.

One of Pat’s other daughters, Debby, famous for her ’70s hit “You Light Up My Life,” was first to get the terrifying news.

“Lindy was vacationing in Spain when it happened,” said the friend, “and she gets a call from her sister saying that Ryan had been in this terrible accident.

“He was so severely injured they didn’t think he would make it.”

For six frightening months, Ryan lay in a coma, needing blood transfusions to stay alive. And years passed before he recovered enough to eat and move around on his own.

As The ENQUIRER reported last year, when Ryan took his first steps, a thrilled Pat declared: “I truly believe that the power of prayer helped save my grandson.”

But the young man was left with a debilitating problem. He developed an uncontrollable fear of men he didn’t already know.

“He feels threatened, so it really limited where we could go,” Lindy, who wrote a book called “Heaven Hears” about her son’s ordeal, told The ENQUIRER. “But if I’m able to give him just a tiny bit of chocolate brownie laced with medical marijuana, which calms his anxiety, then we can take him to church.”

Lindy, who lives in Coto de Caza, Calif., says she’s grateful the state has legalized medical marijuana, proclaiming: “It’s given us a more normal life.”