What is and what should never be: the possibility of playing with super groups that never materialized

It’s cool that Myles Kennedy is part of hard rockers Alter Bridge, which has released six albums since forming in 2004. Hats off to the South Hill vocalist-guitarist for his work with iconic guitarist Slash and Myles Kennedy and the Conspirators.

But what should arguably be at the top of Kennedy’s impressive resume is the band that could be dubbed “what is and what should never be.” A dozen years ago, Kennedy met with the members of Led Zeppelin sans Robert Plant.

Word spread that Kennedy could possibly front one of the greatest bands in rock history. Kennedy, 50, was born the month after the game-changing “Led Zeppelin II,” which includes the song “What Is and What Should Never Be” and was released in 1969.

He happened to be a huge fan of the legendary band while coming of age in Spokane during the 1980s. When Kennedy was invited into the studio to jam with his childhood heroes, he was over the moon.

“I didn’t know what to expect when I went out there (to London),” Kennedy said while calling from his South Hill home where he’s working on new material. “It was an amazing opportunity to jam with those guys.

“To me, Led Zeppelin is the alpha and omega. It was surreal. I had a lot of emotion inside of me when I walked into that studio. I was trying to keep my cool. My inner 14-year-old was freaking out!”

Surreal is how Kennedy, who is currently working on a solo album, explained his experience. Kennedy looked back on the songs he jammed on with guitarist Jimmy Page and multi-instrumentalist John Paul Jones. Kennedy gushed about singing “The Rain Song,” since the gorgeous ballad is his favorite Zeppelin tune.

“I also loved doing ‘No Quarter,’ ” Kennedy said. “During the second verse of ‘The Rain Song,’ John Paul Jones plays that beautiful part on the Mellotron, and the hairs on the back of my neck stood up.

“I got so emotional. I had to turn away after watching him play that part. They were just trying to feel out how they would roll it out so they could share their music.”

It would have been fascinating to see what would have happened if Kennedy and Zeppelin had embarked on a tour. But they are not the only act who failed to launch.

When Van Halen parted ways with vocalist and provocateur David Lee Roth after the “1984” tour, guitar hero Eddie Van Halen asked Scandal’s Patty Smyth to replace the charismatic Roth. The wife of tennis legend John McEnroe passed.

“Joining the band, to me then, ‘Oh God, they fight all the time, him (Eddie Van Halen) and his brother (Alex Van Halen), and I don’t want to get into a volatile situation,’ ” Smyth revealed to ultimateclassicrock.com. “But I regretted turning him down. For a long time, I regretted it. When you start to have regrets, I was like, ‘Oh man, I would’ve made so much money!’ ”

Smyth isn’t the only rocker living in regret. During Metallica’s salad days back in the early 1980s, James Hetfield was reluctant to sing. The band asked Armoured Saint vocalist John Bush if he would front the band. Bush opted to focus on his band.

After Metallica bassist Jason Newsted quit the band in 2001, Hetfield offered his spot to former Ramones bassist C.J. Ramone. However, Ramone opted to focus on his autistic son.

UFO guitarist Michael Schenker says the Rolling Stones wanted him to replace Mick Taylor in 1974, but he turned down Stones legends Mick Jagger and Keith Richards due to their reputations.

So many possibilities that never were a reality, but Kennedy and Led Zeppelin would have been a hot ticket. Fans still clamor and will always hope for some sort of Zeppelin project.

However, it’ll be a heartbreaker of sorts for those waiting around since the best chance for a comeback was with Kennedy a dozen years ago.