"It was too easy"
Metallica guitarist Kirk Hammett spoke in an interview with Sirius XM radio about the solos on the band's new album, "Hardwired... To Self-Destruct." According to the musician, most of his guitar parts were improvised
“Before, I did a lot of preparation, a lot of homework, until I had several ideas. But this time I just made sure my skills were at their best, and the idea was for me to capture the moment, be totally spontaneous, improvise completely, and see what would come out. And it was a very beautiful experience because I had no idea what the solos would turn out like in the end. I had no idea what they would be like.”.
So I went to the studio and just did it. And looking back at all the guitars on the album, I'm kind of amazed by it all because I know it doesn't sound like me to myself, it was just a conscious thing. And there are still about seven or eight solos that I have to sit down and re-learn because it all flowed so much from my head, from my heart, from within. I was a little surprised at how easy it was. It was almost… too easy.”