I know somewhere, some wise-ass will want to take issue, but it can be reasonably argued that electric guitar is the cornerstone of rock and roll. It's not the only element and it doesn't have to be the most important element, but if you wanted to "explain" rock and roll to someone, you might just play them an electric guitar riff.
I bring that up because isn't it funny that the Beatles, arguably the greatest rock band of all time, weren't a great guitar band? They weren't, and I say this as someone who will tell you George Harrison is his favorite Beatle without a trace of irony. I like the "lead guitarist" of a band that didn't know what to do with a lead guitarist most of the time. The "best" Beatles guitar solo might have been the one Eric Clapton provided on Harrison's "While My Guitar Gently Weeps," all of which suggests George was more than just a lead guitarist in the band.
I bring this up because I just got done listening to "Day Tripper," which has one of the Beatles' finest, most memorable riffs. It's like the Beatles go metal! Okay, so it's not. "Revolution" gets us closer to that. "Revolution" is loud and distorted and that's cool. "Day Tripper" has that memorable, snarling lead that McCartney mostly mimics on bass.
The Beatles have a lot of great songs that are great for any number of reasons. They don't have many that are great because of their guitar work. "Day Tripper" is one of them.