The flow of influence usually drips downward, with the dominant rockers of their time inspiring the next. But Tom Petty, who died Monday night from cardiac arrest, was so good that his sphere of influence traveled backward, inspiring the legends who went before him.

Like most young music fans growing up in the ’60s, Petty soaked up The Beatles, Bob Dylan and Johnny Cash. But when Petty and his band the Heartbreakers came to prominence with the strong, cocksure brand of roots-rock heard on albums such as “Damn the Torpedoes” (1979) and “Hard Promises” (1981), the effect was to revitalize the legends he had learned and cribbed from.

The Traveling Wilburys are the perfect example. Petty, who formed the supergroup in his late 30s with George Harrison, Roy Orbison, Bob Dylan and Jeff Lynne, was the relative pipsqueak of the band, which released its first album in 1988. But his presence and songwriting input meant that he not only held his own with the people who virtually built rock, he helped spur them into a new streak of creativity.

It wouldn’t be the only time Petty’s influence went in reverse. In the ’90s, he worked with Johnny Cash on his albums “American II: Unchained” (1996) and “American III: Solitary Man” (2000). The cover albums showcased a revitalized Cash, and featured memorable renditions of Petty’s “Southern Accents” and “Won’t Back Down.”

It went beyond just music, too. Petty often cited Little Richard as a hero, and 1957’s “Lucille” as one of his favorite records. Little Richard (Richard Penniman) evidently thought enough of Petty to officiate at his wedding to his second wife, Dana York, in 2001. That’s how cool Tom Petty is.

His influence on younger musicians is harder to quantify because it spreads so far. For starters, anything you see categorized as “Americana” owes something to Tom Petty and the Heartbreakers.

Even some avowed punk rockers couldn’t resist working with him. Just months after Nirvana had come to an end following Kurt Cobain’s 1994 suicide, drummer Dave Grohl made one of his first public appearances playing drums for the Heartbreakers on “Saturday Night Live.” Petty apparently offered Grohl a full-time gig, but the drummer had something called the Foo Fighters in the pipeline.

Even unconsciously, Petty’s knack for melody permeates pop. In 2014, fans noticed a distinct similarity between Sam Smith’s worldwide smash “Stay With Me” and “Won’t Back Down.”

Instead of throwing a hissyfit or, as is so common today, filing a lawsuit, Petty quietly worked out a deal in which his name was added to the credits, and he subsequently issued a statement saying there were no “hard feelings.”

Petty borrowed plenty, but lent plenty, too.

It’s for that reason that he’ll never truly be absent from the music world. He’ll live on in the flesh and blood of American rock.