Paramore lead singer Hayley Williams has plenty to be thankful for this holiday season: the band landed its first No. 1 album as part of the "Twilight" soundtrack.

"Dude, it's just crazy and it's kinda hard for me to believe," says Williams of the soundtrack's debut at the summit a few weeks ago. "It's really hard for me to imagine [Paramore hit] ‘Decode' is what's fueling the fire of the soundtrack. That's really flattering."

And the soundtrack continues to be a huge seller: it jumps back up to No. 5 on the Billboard 200 this week and in six weeks has sold more than 800,000 copies, according to Nielsen SoundScan, making it one of the top-selling soundtracks of 2008. In addition to "Decode," the Nashville-based rock band contributed another new song, "I Caught Myself," to the soundtrack.

She may not be in love with a vampire, but Williams, a huge fan of the Stephenie Meyer-penned books, could definitely relate to "Twilight" protagonist Bella when it came to writing "Decode." "I just took everything into account, including experiences I've had, so it came out pretty naturally," Williams says.

Williams laughs that despite Paramore's often disenchanted lyrics on such hits as "Misery Business" and "That's What You Get," "I'm obviously not really a bitter person. Like, when we're sitting here talking right now, I'm pretty happy."

But when it comes time to write, she just turns back the clock to an unhappier time. "I push myself through situations I've experienced before, whether it be real relationships or in watching something my friends are going through," she says. "Anyone can sit down and make themselves remember something or think over something they didn't like and it's easier for me to talk about things that I've learned from that were really hard to go through than for me to sit down and write a song about how happy I am. There's definitely songs that we have that are upbeat and a little more positive, but it's therapy for us to talk about the dark and broken sides of relationships."