Guitarist and vocalist Brad Van wants people to know that Droids Attack is more than just another band with a gimmick.

The three-piece, which combines the high-energy genres of punk and metal, used to have a fourth member who appeared onstage in a robot costume, but after he joined the military, the band pushed its live focus toward its heavily distorted riff rock instead of the stage antics.

“A lot of people miss the robot, but if they ask about it, I just say if they want to see a guy in a suit, they should go to Chuck E. Cheese’s,” Brad Van, 34, said and laughed.

Droids Attack will play a free show as part of the Mill’s “4/20 Fest,” which celebrates the underground holiday for the cannabis-loving crowd. Other bands set to rumble the stage starting at 9 p.m. today are Des Moines’ Superchief and Iowa City natives Snow Demon.

The Mill, 120 E. Burlington St., is touting the show as a “stoner-rock onslaught,” but Van doesn’t necessarily agree that his music fits into the category heavily composed of sludgy guitars and gravelly vocals, which is also known for its slow moving pace and gloomy lyrics.

“A lot of stoner rock is kind of boring to me,” he said. “I try to let people know we play faster stuff, too, but whatever. It’s one of those things where what you are and what people end up calling you sometimes ends up being different.”

The Iowa City show is the first stop on Droids Attack’s “southern leg of touring” in support of its latest album, Must Destroy, which came out in February. Van said the record has made waves on independent rock radio and even landed on College Music Journal’s charts.

“It will be our biggest tour and biggest promotion to date,” Van said.

The Madison, Wis.-based rockers have come a long way since Van met up with drummer Tony Brungraber at the guitarist’s retro gaming arcade in 1998. Both shared a love of science fiction and classic gaming and bonded through conversations about Robocop and Starship Troopers.

Eventually, Van and Brungraber formed Droids Attack in 2001, and finally, in 2004, the group recruited bassist Nate Bush to record its début full-length, All Your Chicks Belong to Us. Eventually Van was forced to close down his arcade and put the machines into storage in order to better support his family.

“We practice at the storage space and every now and again, we’ll flip on the Centipede machine and have some fun,” Van said.

While Droids Attack may have strayed away from its robot roots, the band still writes songs about science fiction and other dark subject matter.

“I like to sing about how people are kind of hypocritical and how they all are sort of wired to do themselves in, you know, that kind of stuff,” the vocalist said.

Van said the band also occasionally writes about Steven Seagal, karate movies, and other “stupid s—,” depending on the group’s mood.

The guitarist said the band is looking forward to scouting out new areas of interest while on the road when not playing songs, citing a trip to an action-figure museum in Oklahoma and the world’s biggest truck stop in Iowa as past detours.

“You meet such great people in other cities, so when you’re visiting you’re looking forward to seeing them and you know, see new places, it’s awesome,” Van said.

Snow Demon guitarist Matt Cooper is one of the many friends Van made while on the road. Cooper said he is looking forward to playing 4/20 Fest with Droids Attack.

“They’re a lot of fun, really good rock ’n’ roll,” he said. “It will especially be a blast to get three somewhat heavier rock bands involved at the Mill.”