“Lethal Weapon” is a Christmas movie.

For years, I’ve been saying it’s much more of a Christmas movie than the hotly debated “Die Hard,” but I’ve never fleshed out my case — until now.

The 1987 action classic “Lethal Weapon” opens to the sounds of Bobby Helms’ “Jingle Bell Rock” as we swoop in on a high-rise featuring Christmas lights-rimmed balconies. (Some floors are pitch-black — no lights inside or out — as if to indicate the hopelessness of the nonbelievers.)

The camera zooms in on an apartment with Christmas lights and a tree on the balcony. Inside, a girl (Jackie Swanson) takes a snort of cocaine, staggers to the balcony, climbs onto the railing — and jumps to her death.

Cut to the Murtaugh household on the morning of the 50th birthday of family man and LAPD Sgt. Roger Murtaugh (Danny Glover). There’s a plastic Santa Claus on the roof, lights hanging from the gutters, a wreath on the front door, a tree and Christmas stockings and other holiday decorations inside.

Meanwhile, in a trailer on the beach, in stark contrast to Roger’s morning, Mel Gibson’s Martin Riggs starts his day alone — smoking and coughing, a gun on the pillow next to him, “Family Feud” on the TV.

Not a Christmas decoration in sight.

The first time we see Riggs in action, he’s undercover, making a drug buy — at a Christmas tree lot.

Later that night, Riggs is drunk, mourning his dead wife, as a Bugs Bunny Christmas special plays on the TV. It’s the polar opposite of a wonderful life, and like the desperate George Bailey, Martin Riggs considers taking his own life — but he doesn’t go through with it.

Cut to the police station, where officers are rehearsing “Silent Night.” When Murtaugh first glimpses Riggs, there’s a Christmas wreath in the background.

Murtaugh’s supervisor tells a story about weeping in bed alone the night before and punctuates it by saying, “Merry Christmas.”

Christmas red abounds in “Lethal Weapon.” Riggs wears shades of red throughout, while Murtaugh sports a red tie. Riggs wears red headphones at the shooting range. After a house (with a plastic Santa on its roof) explodes, kids wearing red sit near a red fire truck. A drive-by gunman in a red car tries to take out Riggs. Murtaugh’s wife (Darlene Love) wears a red blouse.

When Riggs steps out on a ledge to talk to a possible jumper, he cynically says, “Merry Christmas,” and tells the guy, “A lot of people have got problems, especially during the silly season …”

The “silly season.” Riggs is the epitome of the nonbeliever.

After he handcuffs himself to the jumper and they take a leap of faith, Murtaugh drags Riggs into a store on its last legs. The window lettering proclaims, “Christmas Sale … Everything Must Go.”

Which pretty much sums up Riggs’ attitude about his own life.

When Riggs frees Murtaugh and his daughter from their captors, he says, “Let’s do what one shepherd said to the other shepherd. … Let’s get the flock out of here!”

Back to the Murtaughs’ block. The hitman Joshua assassinates two police officers, and, as their squad car rolls into a fire hydrant, we see a plastic light-up Santa “looking on” from a window.

Joshua blasts his way into the Murtaugh home. “A Christmas Carol” is playing on the TV. When Scrooge says, “What day is it?” Joshua shoots the TV and roars, “[Bleeping] Christmas!”

But Joshua can’t kill Christmas and hope. The movie continues to play on another TV in the home.

Even when Riggs hands over the bullet he intended to use to kill himself, it’s wrapped in a red velvet bow.

Cue “I’ll Be Home For Christmas” and the end credits.

Besides the references to Christmas, the framing of shots to include Christmas imagery and the key placement of holiday songs, TV shows and movies, “Lethal Weapon” has parallels to “A Christmas Carol” and “It’s a Wonderful Life.”

Like Ebenezer Scrooge, Riggs is a miserable, lonely cuss who snarls at the very idea of Christmas. But with Murtaugh’s help, he receives quite a wakeup call practically overnight and is welcomed into the Murtaugh home for Christmas dinner, just as Scrooge was welcomed into the Cratchit home at the end of “A Christmas Carol.”

Murtaugh is a spiritual cinematic brother to Clarence in “It’s a Wonderful Life.” He is the agent of change helping Riggs realize he shouldn’t end it all, that life is still very much worth living.

And Christmas isn’t just the backdrop for the movie, a la “Die Hard.” It’s a driving force illustrating the vast differences between the lives of Murtaugh and Riggs at the start of the movie — and the catalyst that brings them together by the end.

Christmas is an integral, vital element. Without Christmas, “Lethal Weapon” wouldn’t be “Lethal Weapon.”