When maturity catches up to decibels

Ladytron, led by frontwoman Helen Marnie (above), finished the US leg of its current tour at the Paradise Rock Club Monday night. (JOSH REYNOLDS FOR THE BOSTON GLOBE)

Oh, Ladytron, you're all grown up. It seems like only yesterday when you thrilled hipsters who could pout to your immortal lines: "They only want you when you're 17/ When you're 21, you're no fun." Back in 2003, you were so aloof (coquettish, you claimed) that you prompted a frustrated guy in the back of the Paradise Rock Club to wonder aloud if Boston bored you. You were cold. You averted your eyes from meeting ours. You were the sound and fury of 2002.

What a relief, then, to catch Ladytron at the Paradise Monday night and realize the band is so much more than that. Long after people actually talk about "electroclash" (electro-what?), Ladytron is no longer emblematic of that short-lived genre. It's a fully formed band with a newfound penchant for grinding out heavy slabs of industrial electronic rock.

The British quartet's past two albums have been perfect vehicles for this new sound. "Witching Hour" set the cornerstone for a darker palette in 2005, and the brand-new "Velocifero" burrows even deeper into heavy guitars and impenetrable synth arrangements.

At the sold-out Paradise, wrapping up the US leg of its tour, Ladytron proved it has grown as a live unit as well. Helen Marnie, ever the style maven with her matted-down black hair (the Kinks, circa '66?), has evolved into a real frontwoman. Her voice, rippling out in waves of reverb, miraculously broke through all the commotion, and she took occasional solos on her Korg synthesizer. Hard to believe, but she actually smiled, danced, and pumped her fist in the air during "Seventeen" and "Destroy Everything You Touch." But only a few times.

Mira Aroyo, however, remains as enigmatic and brooding as her thick eyeliner; the most we know about her is that she's prone to recite her vocals in near monotone and seems really excited when she gets to sing in her native Bulgarian on "Fighting in Built-Up Areas." Guitarist Daniel Hunt held forth in the shadows, where he usually lurks and anchors the band. But noticeably absent was keyboardist Reuben Wu, who missed the show because he's ill. (A roadie later told me that Wu was out with chicken pox.)

Hammered out by a beefed-up touring band - which includes a drummer, a bassist, and yet another synth player - new songs like "I'm Not Scared," "Runaway," and "Burning Up" fared best, though it was still fun to hear a throwback such as "Playgirl," from the band's 2001 debut, "604."

The men of Datarock, tumbling around in oversize sunglasses and matching red track suits with hoods, got a lot of mileage from their opening set of frenetic and silly dance rock. They reminded the audience they're from Norway. Funny, I would have guessed my local fraternity.

James Reed can be reached at jreed@globe.com.