Personally, I think Metallica's
Fade to Black may have been influenced, at least indirectly, by Pink Floyd's
Goodbye Blue Sky. The acoustic guitar immediately puts me in mind of Hetfield's melancholy side. Heck, the guitar figure around the 0:54 mark sounds uncannily similar to my ears.
And I don't mean that as a criticism in any way.
In my view, one of the greatest gifts a musician can have is the ability to recognize a diamond in the rough within another artist's work and then transform that spark into something uniquely their own—without crossing the line into outright imitation.
I'm sure many people here are familiar with the similarities often pointed out between David Bowie's
Andy Warhol and Metallica's
Master of Puppets. Again, I don't see that as a flaw on Metallica's part. Quite the opposite. They heard something inspiring, saw its potential, and used it as a stepping stone to create something grand and original.
That's how I look at it, anyway.