DOCUMENTARY has become America's most diverse and fascinating art form in the last 20 years. That's thanks in large part to story-oriented filmmakers like Errol Morris, Steve James, Joe Berlinger, Bruce Sinofsky and Michael Moore, who have broken free of the public-policy-issues ghetto and into the commercial realm where general audiences live.

But they're just the tip of the iceberg. They link with previous generations of documentarians, including Albert Maysles, Don Pennebaker, Gillo Pontecorvo and Barbara Kopple, who have been making supple, informative and vital documentaries for decades. There are many more, yet. And it takes events such as the American Film Institute's Silverdocs festival, now in its second year at the AFI Silver Theatre in downtown Silver Spring (8633 Colesville Rd.), to help us appreciate what they bring to the world: penetrating insight.

Journalists land, report and leave. Documentarians stay, watch and listen. In the end, what they have to offer is frequently deeper than the deadline journalism in newspaper, television and radio. But the opportunities to see documentaries are sparse.

However, at Silverdocs, which begins screening films Wednesday, there will be documentaries (some 70 in all), panel discussions (oh, you always have to discuss documentaries; there's no sitting around and just watching), workshops and festivities. The festival concludes June 20.

Kopple, who made the epic documentary "Harlan County, USA," is the recipient of the fest's first Guggenheim Symposium honor. She will be honored June 19 at 6:30. "Harlan County" will be screened afterward. She will be joined by Maysles, her mentor, who made the landmark "Gimme Shelter," among many other films. And bluegrass musician Hazel Dickens will perform songs from the film at the festival's closing event.

The documentaries are too numerous to outline, but they include "Control Room," a documentary on al-Jazeera that opens commercially a few days later. It will have its Washington premiere at the Silver Theatre Wednesday at 7. Filmmaker Jehane Noujaim and al-Jazeera journalist Hassan Ibrahim are scheduled to attend the screening and symposium.

Also on tap: "In Good Conscience: Sister Jeannine Gramick's Journey of Faith" about the Maryland nun supportive of gay and lesbian Catholics (Wednesday at 5) ; Robert Stone's self-explanatory "Guerrilla: The Taking of Patty Hearst" (Wednesday at 6:45, June 18 at 4:30); Jonathan Stack's "Liberia: An Uncivil War" (Wednesday at 9:45; Thursday at 5); "The People of Angkor" (June 18 at 2:15), made by Rithy Panh, the Cambodian filmmaker whose "S21: The Khmer Rouge Killing Machine" opens Friday at the Avalon Theatre (see review on Page 42); the wonderful "Metallica: Some Kind of Monster" (June 20 at 8:15) about the heavy-metal band and its agonized bid to attain emotional sanity; "Death in Gaza" (June 19 at 12:15) made by James Miller about Palestinian children -- the director was slain by an Israeli soldier during the filming but producer Saira Shah completed the film; and a film about a personal favorite of mine: "Let's Rock Again!," about former Clash front man Joe Strummer, which screens Thursday at 2:30 and June 18 at 9.

In "Let's Rock Again!," which will screen outdoors on the 18th, Dick Rude follows Strummer as he works to build a second career as the front man of the Mescaleros from San Francisco to Japan. After an 11-year retirement from the glory days with the Clash, the fifty-something rocker works hard, literally knocking on radio-station doors to get airplay for his new material. It's a must-see and must-listen for Strummer and Clash fans; but it's also for everyone else. What this movie shows is a personality who's greater than his musical ambitions. Strummer, who passed away last year, was a gentleman who was generous with everyone who crossed his path. He was a touching inspiration, as this film clearly demonstrates.

For more information on the films and the schedule, which also includes short films, visit www.silverdocs.com.

-- Desson Thomson