I never thought of Jimi as metal - I also never got the "Zeppelin is metal" theory so maybe the problem is me. But there are tunes of Jimi's that have a metal attitude, like Can You See Me at Monterey. By that "attitude" metric, even The Who and of course the Fudge could be metal. Personally I consider Wagner to be the father of metal (the overture to The Flying Dutchman seals the deal for me) but I can see where someone thinks Jimi or Blue Cheer or some other band "birthed" metal.
Vinny Martell of Vanilla Fudge just put out a book-—kinda. I got a copy, but apparently his backer got the book done before the China Virus, then backed out, so he doesn’t have $ to publish it.
Jimi said very favorable things about Vinny’s guitar playing.
Vinny was also in the U.S. Navy during the Cuban Missile Crisis & was down in the Caribbean.