Chadwick Boseman is a great actor. That’s no longer anything the world needs to discover. Yet a funny thing happens whenever I get into a conversation about him. I always ask the person I’m talking to if they’ve seen “Get on Up,” and the answer, almost inevitably, is, “No, I missed that one.” Which never fails to stun me, since it’s Boseman’s most audacious and brilliant performance. He plays James Brown, the pompadoured, electric-souled, jive-stepping visionary of funk who revolutionized the music world (and the world at large), and the first thing to say about Boseman’s acting is that you’re forced to reach for the quintessential biopic trope to describe it: In “Get on Up,” Boseman doesn’t just play James Brown — he channels him.

But the second thing to say is: How the hell do you channel James Brown?

He was a force of nature. No one looked like him, talked like him, or moved like him; his tightly wired delirium was a hurricane all its own. So even if you mimic the iconic mannerisms, how can an actor become James Brown?

Boseman does it. Amazingly, he nails the moves — the way Brown would twirl and jitter and shimmy and slice, as if dancing on hot coals. And Boseman, offstage, does an altogether uncanny job of capturing Brown’s cackling imperiousness, spitting out entire sentences as if they were a single word, with a cold gleam that turns every encounter into a chess game, one in which he’s three moves ahead of the person he’s reading.

There’s an entertaining sequence early on in which Brown shows up on a USO tour in Vietnam. The open-backed military plane they’re on gets shot at, but Brown, unlike his band members, isn’t scared (Brown to the pilot: “James Brown was born dead! And I breathed. Y’all didn’t take me then, and sure ain’t gonna call me back right now!”), and once they’re on the ground he harangues the USO officer who dares to apologize for the “plane trouble” (“Plane trouble? They try to kill James Brown today! You want to go down in history as the man who killed the funk?”). His voice is gruff, with a fair amount of gravel in it, sailing into that signature high-pitched wail, but the key to his ripely loquacious fury is that the more out of control he sounds, the more in control of every moment he is. As Boseman plays it, Brown’s personality is a series of masks he wears to get what he wants.

“Get on Up,” which came out in 2014, was the first film directed by Tate Taylor after “The Help,” and it’s the movie in which he upped his game and became a world-class filmmaker. It was my choice for best movie of the year, and for good reason: It’s dramatic and exhilarating, with the pulse of an incendiary musical, and as scripted by Jez and John-Henry Butterworth, it’s one of the most historically accurate of all biopics. (Just watch Alex Gibney’s terrific documentary “Mr. Dynamite: The Rise of James Brown” if you doubt it.) Yet there’s a hard-won poignance to it as well. A scene set backstage at the Apollo Theater between James and the mother who abandoned him, played by Viola Davis, will tear you apart.

The movie was a late-summer release (it opened on the same day as “Guardians of the Galaxy”), and it carved out $30 million at the box office, yet given Boseman’s standing today I now think of it as a bit of a lost film. “Get on Up” doesn’t have nearly the stature it deserves. It’s a knockout of a movie built around a feat of acting as heady and transformative as those in the best biopics of our time — the equal of Jamie Foxx in “Ray,” Gary Oldman in “Sid and Nancy,” Philip Seymour Hoffman in “Capote,” or Angela Bassett in “What’s Love Got to Do With It.”

The drama is straightforward, with subtle layerings in time, so that you see how the agony of Brown’s upbringing — shunted aside by both his parents, slammed in jail for years for stealing a suit — shadowed everything he did, including the invention of funk. His childhood was etched in fire, and it made him a solo vessel, a high-flyer who became a musical revolutionary but also a petty tyrant, treating his band members as if they were beneath him. (They were his friends, but he fined them for infractions, made them rehearse on days off, and ordered them to call him “Mr. Brown.”) The film is uncompromising in its depiction of the cruelty Brown was capable of. At the same time, it’s a dazzlingly complex portrait — we see his rapture, his calculation, his violence, his showman’s bravado, his business acumen, his social awareness, his buried broken heart, and his obsession with funk as a faith that he created.

It would be hard to think of another movie that dramatized, this vibrantly, the complicated roots of African American popular music — how Brown was activated by the wildness of the passion he saw in church, by the power of sin, by the bliss of gospel, by the racial violence that surrounded him. There’s an astonishing scene in which, as a kid, he’s placed in a boxing ring, blindfolded, for the entertainment of a white country club, and when he’s laying on the canvas, semi-knocked out, he fixes on a musical phrase from the jazz band that’s playing and fashions it, in his imagination, into a cold, hard, repetitive pattern. It’s the birth of funk — as music, and as a kind of protective weapon. It’s a sequence that adds a simulacrum of meaning to everything we see Brown do onstage. His dancing is ecstatic, but part of the power of it is that he’s stomping on the evil, transcending it, killing it with his moves.

When “Get on Up” came out, Boseman had just one major movie to his credit: “42,” in which he’d established himself as a formidable actor with his performance as Jackie Robinson. So when I saw “Get on Up” again recently (the first time I’d revisited it since 2014), I was curious to see if Boseman’s performance would look any different, since I’m now so familiar with who he is. He’s the kind of subtle and deliberate actor who leads with his mind. That’s part of what made him so singular in “Black Panther” (where he infused a comic-book hero with the spirit of a shaman), and in Spike Lee’s “Da 5 Bloods” every time he shows up in flashback his quiet intensity burns a small hole in the screen. Boseman’s persona, to the extent that an actor who’s this startling a chameleon has one, is sly and pensive, with a touch of reserve. Whereas James Brown was a walking volcano, a Dionysian spirit.

But in “Get on Up,” damned if Boseman, with his Apollonian aura, doesn’t become Dionysius in a soul-man coif. What’s religious about the James Brown we see here isn’t just the music. It’s his sensation of destiny — his own destiny, and the destiny of funk as the new heartbeat of the world. Funk was a revolution that turned the rhythms of rock ‘n’ roll upside down (that’s why it laid the foundations for disco and hip-hop). And in “Get on Up,” Boseman’s James Brown parades the glory of funk with an outrageousness that makes him a master of the universe. Yet he’s always aware of the structure he’s upending. Near the end, there’s a looking-back montage, and for a moment we see James as a kid saying, “I paid the cost to beat the boss.” At every step, the film takes the measure of what it meant for James Brown to come out on top of a universe he never made. As Boseman plays him, he’s a creator and a genius, a man who knew how to feel good but took no prisoners, and the closest thing there is to a true-life superhero.