When it comes to addressing tragedy and hot-button social issues, director Gus Van Sant has plenty of experience – his previous films have addressed topics of school shootings, suicide and inner-city education – so it’s a no-brainer that he would take on writer Dustin Lance Black’s “Milk,” a biopic of New York lawyer-turned-San Francisco District Supervisor Harvey Milk.

Sean Penn stars as Milk, the first openly gay man elected to major public office in California, who became a hero of America’s gay community in the mid-70s before fellow supervisor Dan White murdered both Milk and Mayor George Moscone at San Francisco’s City Hall.

Penn’s performance is the obvious highlight of the film. This is not the usual surly, aggressive Penn role like those in “21 Grams” or “Mystic River,” or the helpless titular character of “I Am Sam.” Penn and most of his supporting cast, which includes Emile Hirsch, James Franco and Diego Luna, are ferociously, fearlessly gay. Van Sant wisely includes a few clips of the real Milk, and not only does Penn look like the slain supervisor; he mimics Milk’s soft voice and feminine mannerisms perfectly. Milk was well-known for his silliness and sense of humor, and Penn seems to relish the chance to lighten up what might have been a dour and self-righteous biopic.

Thankfully, Van Sant sets a fast pace from the beginning and doesn’t let the story bog down into melodrama or dry documentary. Penn gets to deliver a sassy one-liner; in one scene during a race for the California State Assembly, Milk tells his conservative heterosexual opponent, “I’m looking forward to licking you… in the polls.”

Hirsch, Franco, Luna and newcomer Alison Pill, as Milk’s closest confidantes, advisors and lovers, are equally invested in their roles. Especially with Penn, their dialogue and on-screen camaraderie is sharp and witty, keeping the movie funny and entertaining even in the rare scenes that don’t include Milk himself. The large group of supporting actors is well-cast, and most actually look like the real people the roles are based on.

In inevitable contrast to another (perhaps the other) major Hollywood movie about gay men, “Brokeback Mountain,” these characters have no doubts about their sexuality. All residents of San Francisco’s now-famous Castro district, they are out and proud, not to mention politically active. While nudity is kept to a minimum, Van Sant isn’t shy about a little man-on-man action, and those excited by the thought of a shirtless James Franco or Diego Luna will not be disappointed.

In another excellent casting decision, “No Country For Old Men” star Josh Brolin brings quiet intensity to the role of fellow district supervisor and Milk’s assassin Dan White. Though Brolin spends a relatively short amount of time on screen, his portrayal of White as antagonistic and embittered is one of the best performances in “Milk.” It’s clearly understood that whatever White’s motives, his crime was one of passion at least as much as one of hate. Brolin captures this throughout with a wincing, pressured expression, just barely discernable behind his friendliness towards Milk, and his hints at instability in “Milk”‘s third act are chillingly foreboding.

Altogether the film is more than entertaining, and though it occasionally wanders over the fine line between biography and documentary – Milk’s political enemies, especially fundamentalist Christian singer Anita Bryant, come off flatly – “Milk” will certainly remind viewers that history repeats itself. With the recent passage of Prop 8, Van Sant’s film couldn’t have been released at a better time, and the performances by Penn, Brolin and with the supporting cast already drawing raves from indie enthusiasts and Oscar speculation from some in the mainstream media, “Milk” should not be missed.