In case you guys didn't hear, the guitarist from Slayer died.
RIP
I find it hard to believe that someone would actually ask this OP question though...
Back when I was young, it kind of went without saying. In fact, early heavy metal was actually called acid rock.
Who didn't trip listening to Sabbath and Zeppelin... Rush? People would trip at shows. Of course, the definition of what is and is not Heavy Metal was looser then. (Bands as un-metal by today's standards as Santana & Jethro Tull were considered part of the whole thing then... even early Queen!)
And no-one had started growling and going all Death oriented yet.
Watch the movie Heavy Metal if you don't believe me.
Even when it got kind of glam it was still fun to trip to. I remember seeing Maiden, AC/DC, Van Halen, Ozzy, Metalica, Dio, QueensrĆæche, Yngwie etc. while tripping balls and loving it.
I generally preferred the more progressive stuff and psychedelic or jam stuff for tripping, though. As hard as it is for the young people today to imagine, rock & roll was the heart of the drug culture for a loooong time before samplers and sequencers were invented. Bands like Floyd and the Dead were institutions of psychedelia. And I am still usually more excited about the latest Primus or Phish disc dropping than any of the nameless multitudes of electronic producers stuff... I can say that because I produce electronic music myself.
Nothing quite like a loud electric guitar to give you crackling electronic waves of psychedelic joy, though.