Loverboy is this year's Cinderella story. In less than two years, they have transformed themselves from an unknown Canadian group in the Journey-Foreigner-REO-Styx mold to one getting equal billing on that platinum plateau. They have moved from striking no responsive chord to instant, one-chord recognition for the AM-radio fodder they've dished out over the course of two immensely successful albums. At the Merriweather Post Pavilion on Saturday, they had 10,000 screaming fans clapping away to hard-driving, melodically adroit rock 'n' roll.

Like any well-tooled machine, Loverboy gets good mileage out of a powerhouse engine with all the standard features--Paul Dean's showboat lead guitar, drummer Matt Frenette's piston-steady drumming and Mike Reno's high-pitched vocal wheelies. The band plays in four basic forward gears. The resultant music is a bit more mindful than heavy metal, a bit more mindless that power pop; for mass radio, it's manna with a beat.

At the Pavilion, the musicians paid tribute to themselves by playing virtually everything on their first two albums "for all the people who like to rock and roll hard." The best songs were also their biggest hits--the anthemic "Kid Is Hot Tonight," the chunky "Waiting for the Weekend" and "Turn Me Loose," the hard and hook-laden single that blew Loverboy to the top of the heap. But things did get samey after a while.

The only truly dull moments came when Loverboy's vocal-oriented delivery succumbed to ham-fisted instrumental solos. It was a problem that also occasionally plagued Huey Lewis and the News, but the California sextet turned in a generally commendable opening set that proved it has made the jump from bar to concert band as smoothly as a jump from beer to whiskey: The ultimate good-timin' effect is similar, it's just the kick that's so much stronger and immediate.