There's no question Metallica's sophomore album,saw the band finding their thrash metal stride with better songs and production than on their stunning debut

And a big reason the songs got better and were more mature, for lack of a better word, on Ride was because of bassist Cliff Burton's influence. The legend had a bigger hand in helping write more songs (he only got writing credits for "Anesthesia - Pulling Teeth" from Kill 'Em All. Tracks like "Fight Fire with Fire", "For Whom the Bell Tolls", "Ride the Lightning", "Fade to Black", "Creeping Death" and, of course, "Call of Ktulu" were co-written by Burton, who died tragically in a bus accident in Sweden on Sept. 27, 1986.

Guitarist Kirk Hammett recalls in an interview with Guitar World how Burton was the guy who had the musical theory and brought his love of harmonies to the songs.

"Cliff studied music in college,” Hammett said. “I had a grasp of music theory, thanks to Joe (Satriani, who was teaching Hammett ahead of recording Ride), but Cliff went the whole length and learned musical theory and everything. And he was way into harmonies. James really absorbed the dual-harmony thing and took it to heart. He made it his thing, but it was originally Cliff’s. Cliff also inspired James greatly on counterpoint and rhythmic concepts."

Interestingly, Hammett recalls a memory of Burton singing along with the Eagles whenever they came on the radio.

"And he would also sing harmonies. I remember the Eagles would come on the radio and he would sing all the harmony parts, never the root," Hammett said.

As for Burton's work on Ride the Lightning, it was often a case of the bassist throwing in some key parts here and there, while helping the band create harmonies and different feels.

"He wrote that “Creeping Death” harmony part and the harmony in the intro to “Ride the Lightning.” He even helped me with a lot of the harmony stuff I played in the solo to “Ride the Lightning," recalled Hammett. "I remember, I thought he’d just grab a bass and show me. But no, he had me write out all the notes in my solo on a piece of paper. Then he grabbed a pencil and went through and notated it, "If you’re playing E, then G, then A, then C…" I’m looking at him like, What? But I took the paper and worked it all out. And you know what? It was perfect."

Hammett: "Cliff was a Total Anomaly"

Hammett recalls his former bandmate being an eccentric type when it came to music.

"Cliff was a total anomaly. To this day, I’m still trying to figure out everything I experienced with him. He was a bass player and played like a bassist," said Hammett. "But, fucking hell, a lot of guitar sounds came out of it. He wrote a lot of guitar-centric runs. He always carried around a small acoustic guitar that was down tuned. I remember one time I picked it up and was like, "What is this thing even tuned to, like C?" He explained that he liked it like that because he could really bend the strings. He would always come up with harmonies on that acoustic guitar. I would be sitting there playing my guitar and he’d pick up his bass and immediately start playing a harmony part."

That memorable, soft acoustic intro to "Fight Fire with Fire" was a piece of Burton brilliance that opened the album, lulling listeners before the heavy guitar kicks in.

"That acoustic piece was Cliff’s! Cliff wrote that on the down-tuned acoustic guitar I was talking about. He had a really good grasp of playing the guitar, and a good grasp of classical modulations. That intro was his piece," said Hammett. "We heard it and stuck it onto “Fight,” and it worked fantastic. We knew that was going to be the opening track. There was no question about it."

Not only was Burton a phenomenal bass player, but he was such an integral part of Metallica's songwriting on the Ride the Lightning, then on 1986's Master of Puppets, the last album he'd do before his untimely death at just 24 years old.

Check out five of the five best Metallica songs co-written by Cliff Burton