“The sun’s in my heart and I’m ready for love.”

When I think of Singin’ in the Rain, I think of unbridled joy; there is a vibrant optimism to this classic movie musical that remains nearly unmatched in cinema history. It’s hard not to smile along with Gene Kelly as he splashes around in puddles and clings to a lamppost while singin’ the titular song (“come on with the rain — I’ve a smile on my face”). Humor is baked into nearly every scene and inventive scenario — from microphone placement gags during production of the movie-within-the-movie The Dueling Cavalier to the audio going out of sync in the most hilarious possible way during a test screening of that disaster of a film, to the gleeful way in which Kelly and Donald O’Connor make fun of a dialect coach’s verbose exercises in song (“Moses supposes his toeses are roses, but Moses supposes erroneously”) before breaking out into a frenetic, joyful tap dance. There’s the spontaneous laughter of the delirious Kelly, O’Connor, and Debbie Reynolds after the happy final refrain of “Good mornin’, good mornin’… we’ve gabbed the whole night through.” There’s even plenty of slapstick humor — most notably during Donald O’Connor’s absolutely stunning, acrobatic song-and-dance number “Make ‘Em Laugh,” which sees the star running into backflips off of set walls, being carried on a plank by two stagehands, dancing with a rag doll mannequin, and crashing through drywall.

There is also, of course, the slapstick humor of Jean Hagen’s Lina Lamont getting a pie thrown in her face.

Because of all of this, it’s easy to forget how dark the plot is at times. Singin’ in the Rain is a decidedly not-flashy look at an old Hollywood in transition, as silent film stars (like Kelly’s Don Lockwood and Hagen’s Lina Lamont) and many studios find themselves unable to adapt to the advent of talking pictures. Beyond that, the life of an actor isn’t portrayed as glamorous; Don regales his fans at the beginning of the film with a speech about how the one constant throughout his career has been that he’s always held on to his dignity… and as he speaks, we see flashbacks of a decidedly un-dignified journey to super-stardom. Meanwhile, the studio hypes up a romance in the public eye between Don and Lina; Lina buys into it, but Don hates her too much to even pretend that it’s true.

Meanwhile, a young woman (Reynolds’ Kathy Seldon) has moved to LA to become a serious actress, but the first time that we see her perform, she’s jumping out of a fake cake to join a line dance for a bunch of suits (“all I do is dream of you the whole night through…”). Then, once Kathy gets a chance to have roles in movies, the aging Lina sees her as a threat and tries to bribe the studio head to ruin her career before it starts.

If this is the story, why do we walk away from almost every scene feeling hope and joy?

Part of the secret is, of course, the dynamic performances of Gene Kelly, Donald O’Connor, and Debbie Reynolds, all of whom radiate happiness in this movie — they look like they’re having a blast in every scene.

But the rest of the overwhelming positivity comes from the lyrics of the songs and the attitudes of the characters who sing them.

Take “Broadway Melody.” The sequence itself is a lengthy diversion from the main story — you could easily dismiss it as self-indulgent showcase for Kelly’s dancing skills as opposed to an integral part of the narrative — but in its own unique way, it sums up the entire movie. Kelly plays a version of his Don Lockwood character in this sequence — or, perhaps more accurately, a hybrid between Don Lockwood and Kathy Seldon.

Through song and dance across many theatrical sets, he reveals how desperately he wants to be a Broadway star (“Broadway rhythm’s got me…”). His character shows up at a talent agency wearing nerdy glasses and a suit that is hardly the height of fashion; he knocks on a door to the beat of the music, is rejected, and promptly moves on to a door down the hall. He knocks on that door, is rejected, and moves on to the next one. An agent finally gives him a shot, and he performs on an off-Broadway stage. He tries to win over a woman in the audience there, and she rejects him, too.

Rejection keeps coming his way, but he keeps pushing forward in spite of it. Why?

Well, “gotta dance, gotta dance, gotta dance,” he sings with a smile.

There’s not a negative lyric in any song. Even when characters doubt themselves — like when Don needs reassurance that he’s actually a good actor — they don’t stay down on themselves for long. Their relentless optimism keeps them happy, even when life gets them down. They don’t dwell on what isn’t right, and when things get tough, they have their friends to lean on the whole night through.

For Don Lockwood, it doesn’t matter that he’s out in the streets, caught in the rain. He’ll still sing and he’ll dance… because he’s in love.