Heavy rock is bleeding into other genres. This is the easiest way to dispatch notions that heavy metal is weird, strange, or different. There is an aesthetic and culture related to heavy rock that is comparatively uncommon, but the music attaches to the trends, not the other way around. Broken down, the distinct sounds and techniques of heavy rock music are very common.
On the one hand, this is inevitable because everyone is to an extent using the same equipment.
Consider Black Sabbath's recording of "War Pigs" here, a fundamental heavy metal track. Tony Iommi's guitar solo around 3:28 is very similar to the sound from Paul Kossof's guitar on this recording Free's "Mr. Big," with the solo at 2:33.
Free isn't typically thought of as heavy rock, but even if they are, they aren't the progenitors of heavy metal that Black Sabbath are. But notice how similar the solos are. The guitar tones nearly identical: Gibson guitars with humbucking pickups through Marshall amplifiers. The contents of both solos feature stock blues licks and familiarity with the minor pentatonic scale, but you can also hear both players experimenting with the complexity of the natural minor scale by adding the 2nd interval, which is indicative of guitar players of this time forging a new musical identity beyond the blues (you can hear early recordings of Peter Frampton with Humble Pie trying to sound sophisticated by playing anything but blues licks. He nailed it later). These natural minor licks tend to be a little more hesitant, probably because the players are relishing the novel sound, and because once they hit that note, they may not know where to go next.
Or at least that's what happened to me when I first learned about the Dorian scale.