Chadwick Boseman flat-out nails his performance as James Brown in “Get On Up.” (D Stevens/D Stevens/Universal Pictures)

In last year’s “42,” Chadwick Boseman played baseball legend Jackie Robinson as a man suppressing his pride and bottling up his anger. It was a portrayal of understated dignity that was all about emotions being swallowed and words that went unsaid. In “Get On Up,” Boseman gets the chance to turn into another African American icon: James Brown. This time, the Howard University graduate takes everything he held in check in that previous role and lets it loose in a firehose of charisma, determination, fury and unbridled funkiness.

Boseman flat-out nails the Godfather of Soul in this long-awaited biopic. He struts around with Brown’s signature blasé-rooster swagger, smiles with enough brilliance to make a blind man squint and glides across various stages as if the soles of his shoes were coated with slick glass. But perhaps the most crucial thing he gets right is Brown’s speaking voice; when Boseman talks, his words pour forth in a raspy stream, as if they’ve been run through a mesh strainer, then doused heavily with freshly ground black pepper.

One could describe Boseman’s performance in “Get on Up” as electrifying, and that would not be wrong. But it’s more accurate to say that watching Boseman transform into James Brown, who died in 2006 at 73, is like watching a dude invent electricity while the idea for electricity is still occurring to him. Tate Taylor — the director of this film, the follow-up to his 2011 late-summer hit, “The Help” — needed a vibrant, convincing Brown to make this movie work. Lordy, oh lordy, did he get one.

(Related: Chadwick Boseman jumps, sweats and splits into character as James Brown)

But that doesn’t mean that “Get on Up” succeeds entirely, entertaining as it often is. Taylor and screenwriters Jez and John-Henry Butterworth make the understandable error of trying to cram all, rather than just some, of Brown’s life into a single movie. Even though “Get on Up” skips over a number of details in the Brown biography — including the existence of two of his four wives and several of his arrests for assault and domestic violence — the film still feels overstuffed and overly long.

Rather than telling the story in standard chronological order, Taylor and the writers drop the needle on various, out-of-sequence grooves in the Brown timeline. The film opens in 1988, when Brown fires a shotgun into the ceiling of one of his own office buildings, a moment that would eventually lead to a police chase and Brown’s arrest. The narrative then hopscotches backward and forward through the decades, from sepia-toned flashbacks of Brown’s painful childhood to triumphant, goosebump-inducing performances in Paris circa 1971. Taylor also allows Boseman’s Brown to frequently break the fourth wall and speak directly to camera.

All these cinematic acrobatics can be disorienting, but there are moments when Taylor’s approach gives the film a fizzy energy that feels fresh and right, particularly in one scene when Brown’s manager, Ben Bart (played by Dan Aykroyd, who appeared with the real James Brown in “The Blues Brothers”), starts explaining to Brown how the recording industry works. Brown abruptly stands up, walks away from the table where the two are eating lunch, then discloses to the audience how he plans to recruit DJs and young fans to spread the word about his upcoming live gigs, which could prove far more lucrative than mere record sales. He then strolls back to the table, where Bart’s still running his mouth, completely unaware that Brown has already made up his mind about how to handle matters.

It’s a bold and fun illustration of the theme driven home a bit too bluntly throughout “Get on Up”: that James Brown was conditioned from birth to look after James Brown, a self-preservation technique that made him a massive success, but also ruined relationships with his bandmates, his best friend Bobby Byrd (Nelsan Ellis) and the many women he abuses.

These kinds of Hollywood pop stardom portraits usually flop or fly based on their casts and the ebullience of their musical scenes. “Get on Up” wins on both fronts. Boseman’s performance is complemented by Ellis’s rock-steady portrayal of Byrd, as well as strong work from two of Taylor’s reliable “Help” alums: Octavia Spencer, who plays Brown’s brothel-owning aunt, and Viola Davis, who, as Brown’s neglectful mother, swoops in for the film’s most emotional scene and knocks it straight on out of the park.

As for the music, Brown’s key infectious booty-shakers — from “I Got the Feeling” to “Cold Sweat, Pt. 1” to “Get Up (I Feel Like Being a) Sex Machine” — are represented, with Boseman effectively busting moves and lip-synching seamlessly to original James Brown tracks. Boseman brings every snippet of a JB show to life with sizzle and snap.

Ultimately, that’s what Brown’s fans may crave most from this tribute to the artist who invented superbadness: a movie that does justice to the man’s funk. Watch Boseman for even a minute and, as the song “Superbad” says, it’s clear: He’s got it.

Chaney is a freelance writer.

★ ★ ★

PG-13. At area theaters. Contains sexual content, drug use, some strong language and violent situations.
139 minutes.