After spending part of the summer with the likes of Henry Rollins, Pennywise and Rancid on the Warped Tour, Sum 41 [ tickets ] shouldn't be nervous about performing with anybody.

But Cone McCaslin, bassist for the Canadian punk-rap band Sum 41, admitted that he's a bit intimidated by Unwritten Law, which is opening for his band on its first headlining tour of the United States.

"They've been around for awhile," McCaslin said. "Longer than we have. I thought they were going to smoke us. Well, they are smoking us. But I think we're doing OK."

Generally speaking, Sum 41 is doing better than OK. Its latest album, "All Killer, No Filler" (Island/Def Jam), debuted at No. 23 on the Billboard 200 album chart dated May 26. The album went platinum, mostly thanks to the successful, bratty single, "Fat Lip."

McCaslin took time out to talk to liveDaily about "All Killer, No Filler," playing with former Judas Priest frontman Rob Halford and ex-Motley Crue drummer Tommy Lee at MTV's 20th birthday party and crossing the U.S.-Canadian border since Sept. 11.

When you decided to name your album "All Killer, No Filler," did you realize that that was just providing fodder for music critics who either liked or disliked the album?

Oh, yeah, that's partly the reason we did it. We like stuff like that. We always read bad reviews or bad interviews when writers don't like us. We're gonna make shirts of good quotes from writers who don't like us: "Sum 41 better learn to play their instruments before they do the choreography bulls---."

Well, all you can really do is laugh. But that must have been a thrill to play with Tommy Lee and Rob Halford at MTV's 20th anniversary show.

That was probably the single most stacked time of our whole musical career yet. We had a day by ourselves [to rehearse] and a day with them, and the next day we played. Rehearsing with those guys, it was just crazy. Tommy Lee's more of a kid than we are. He's very hyper and he's always pumped up. He burst through the doors when we were just sitting there waiting for him. He comes over, he's hugging us all--we don't even know him yet--he's giving us hugs and telling us how pumped he is to do this, and we're like, "Holy s---. This guy's the real deal." Covered in tattoos. He's the coolest guy.

What did you learn from playing with those two?

Well, Tommy Lee gave Steve [Jocz, drummer,] a couple drum lessons while we were rehearsing. There were a couple beats he was playing that Steve was just like, "What the hell are you playing?" He came over and showed Steve the kick patterns. Steve learned a lot from him.

Rob Halford, I don't know. He's crazy. He can still sing. I think he sings better now than he did back then. When you listen to his albums, back in Judas Priest, it was awesome. But when he came and just sang live, we all turned our heads, and we were just smiling ear to ear. He sounded just like the album and even a little better.

How were you chosen to perform with them?

We kind of asked them to do it. We were booked to play the 20th anniversary. We were going to do a metal kind of medley. We found out that Tommy Lee and Rob Halford were going to be there. We thought we should ask them if they'll play their songs with us. Tommy knew the band and he liked us. He said yes right away. Rob didn't really know the band too well so we sent him all the stuff and the video. He's like, "Oh, yeah." I never thought we'd get the respect of people like that.

Do you think playing with them added a lot of credibility to your band?

Um, I don't know if it did. Maybe it did. I can’t really tell things like that. I hope people think of us as a serious band. A lot of people are saying that playing with Tommy Lee and Rob Halford, people are gonna take us really seriously now. I hope that happens because we don't want to be known as a novelty band that's going to go away. We want to be around for awhile.

Your band features three singers, something that's a rarity these days. There aren't very many bands of singers.

Yeah. [laughs] Three different rappers. [laughs]

There hasn't been much of that since, maybe, Beastie Boys. It adds a lot of punch to the music.

Yeah, we like all that type of music. We grew up on old-school hip-hop. Dave [Baksh, guitarist,] was in a death-metal band, so he's the guy who turned us all on to metal. Growing up in high school, the Southern California punk rock stuff was really big. We all were into that. We all liked all that music, and we just have to find a way to play what we like all into one. When we play live, we'll go into a hip-hop thing, and then we'll play metal, then we'll play a fast song. We just like to do it all. It keeps the fun in it. For me, it's all fun to play all different kinds of music.

It keeps it fresh, as opposed to playing the same thing day after day.

Every day is different in our show. Things happen and things get a little weird sometime. It's never the same show.

Describe the songwriting process in Sum 41.

Normally, Derick [Whibley, singer-guitarist,] will write the music--not, like, our parts, the guitar parts--and he'll come up with melodies. Lyrics are normally the last thing ever to come. He'll write that part, the melodies, whatever works. Then he'll bring it to us. I put the bass down, all the guitars, and he [Whibley] has a drum machine, he puts it over the top. He'll bring it to us and show us the song. I can add a part here, here, here and here. We'll come up with our own parts. Derick normally writes the lyrics when the whole song is completely done.

Considering you're from Canada, did the Sept. 11 terrorist attacks change your view on touring in the United States?

When that happened, we were in Los Angeles on the Blink-182 tour, and we had four shows left. We, like, canceled the rest of the tour and went right home. We were home for about 10 days, and they made us go over to Europe. We kind of agreed to. We figured, "We can't stop being a band. We have to work right now. We can't take time off right now." We chose to go over there. I think we're even going to go back in November. It's a little more serious now than when we went over--we've started to bomb Afghanistan. Every time I walk on a plane now, I'm eyeing everyone down now: "It could be you." I'm freaked out flying nowadays, to tell you the truth.

How did you get over being nervous?

I'm not over it yet. It's scary right now.