We all know the Beatles were the biggest influence on people like Ozzy Osbourne and Gene Simmons but the Beatles did have a influence on Heavy Metal.
Of course they did not invent Heavy Metal and there were others more influential but they played a part from popularizing feedback on "I Feel Fine" to lead bass fuzz distortion on "Think For Yourself". Both huge elements in Heavy Metal
Even some of the Beatles earlier songs like "It's All Too Much" recorded during the Sgt Pepper sessions now listen the feeback at the start and the guitar sound. The Beatles. The popular Hendrix chord with it's distortion sound was done on "Taxman" before Hendrix and it was rumoured to have influenced Hendrix "Purple Haze".
"Helter Skelter" uses drop tuning with power chording. The distortion sounds on "Revolution" was very dirty sounding and the Mother Superior part on "Happiness Is A Warm Gun" screams Black Sabbath. Black Sabbath was influenced by the dark and gloomy fade-out section of the Beatles "I Want You" which can be called proto-metal.