Under a Golden Arch, Sincerely U2

Truth battles packaging in U2's Popmart tour, the stadium spectacle that the band unveiled here on Friday night at the Sam Boyd Silver Bowl. The package is high-concept, high-tech razzle-dazzle: a superstar band shows off its big-budget prerogatives and flaunts its status as a consumer product.

But the songs, new and old, tell a different, more introspective story, about private struggles to find faith and purpose. With the Popmart tour, U2 seeks to reclaim its old sincerity using all the artifice at its disposal.

The stadium here, with its 38,000 seats sold out, was one of the smaller stops on the tour. For most of its 14-month, 80-city schedule, U2 will perform in places with more than 50,000 seats, including the show scheduled for May 31 at Giants Stadium. To please such large audiences, U2 provides visual pyrotechnics performing in front of a 170-by-56-foot video screen, under a 100-foot golden arch, next to enlarged cocktail accoutrements: a 40-foot-high lemon and a 12-foot-wide olive on a towering toothpick.

Popmart without the ''m'' is Pop Art, so to accompany various songs U2 has adapted images from Roy Lichtenstein, Andy Warhol, Keith Haring and other artists who made commercial materials their own. Animated graphics on the video screen repeatedly showed humans as shoppers, and the golden arch self-consciously defined U2 as a product being marketed worldwide. In fact, the band has been merchandised with impressive skill. Its current album, ''Pop'' (Island), was No. 1 in 27 countries the week it was released. And on Saturday, the night after the tour's first show, U2 was the subject of a relentlessly promotional prime-time ABC-TV special. At a time when the recording business faces diminishing sales, U2 doesn't shy away from the hard sell.

While the tour plugs ''Pop,'' U2 has also set out to top its own Zoo TV tour in 1992-94, which redefined stadium concerts for the 1990's. In that production, U2 presented itself as part of a media overload, treating the band as one of many competing signals, real and simulated. With that tour and its two previous 1990's albums, ''Achtung Baby'' and ''Zooropa,'' U2 broke away from its 1980's role as a band of painfully earnest idealists. Late in the show Bono, U2's lead singer, appeared in a gold lame suit, sunglasses and devil's horns, as a character he called Macphisto.

In the Popmart production, Bono is back on the side of the angels, or trying to be. On Friday night, U2 arrived at the end of a set of disk jockey dance music by Howie B, one of the producers of ''Pop.'' The 1979 novelty hit by M, ''Pop Muzik,'' segued into the pulsating electronic rhythm of ''Mofo,'' from ''Pop.'' But the first words of that song were, ''Looking for to save my save my soul.''