“Thor” is crammed to the gills with excitement and action, but its overarching symbol isn’t the God of Thunder’s magic battle hammer, Mjolnir. It’s the bridge.

There’s the kaleidoscopic Rainbow Bridge connecting the Norse gods’ home Asgard to the other Eight Realms. There’s the inter-dimensional wormhole studied by a lovely astrophysicist in Puente Antiguo (“old bridge”), N.M. There are the parallel plots connecting two families under siege, and the bond between old legends and comic books. And there’s the film itself, a gateway to 2013’s multihero mashup “The Avengers.”

Happily, “Thor” feels specific and complete, less an obligatory link in an ongoing tale than a handsomely engineered, hugely enjoyable standalone.

Despite the weight of antique myth piled atop it, the film has an agile, buzzing vitality. Chris Hemsworth plays Thor, the temperamental son of supreme ruler Odin (a majestic Anthony Hopkins) and brother to Loki (Tom Hiddleston) who thinks, often deviously, before he acts. The long truce between the Frost Giants and the gods wobbles when several titans invade Asgard to reclaim their power source, held by Odin as spoils of war. Hotheaded Thor escalates the conflict with a rogue reprisal attack. In its aftermath, he further angers Odin (never tell a god “You are an old man and a fool!”)

Banished to present-day Earth to wander the desert, stripped of his powers and his hammer, Thor is sideswiped by a speeding van. Inside are scientist Jane Foster (Natalie Portman), her mentor, Erik (Stellan Skarsgerd) and wry sidekick Darcy (Kat Dennings), whose squabbles are a funhouse reflection of the gods’ discord.

For much of the film Hemsworth is both hero and comic relief. He doesn’t walk, he strides. He doesn’t speak, he proclaims. With vainglorious Viking swagger, Thor smashes his coffee mug in a diner, bellowing “Bring me another!”

His clashes are more dramatic, and bruising, with agents of SHIELD. The spy agency has confiscated Jane’s research and cordoned off the impact crater around Mjolnir, now immovably fused to a boulder. Thor’s one-man assault on the heavily guarded complex is a textbook example of kick-butt action moviemaking. Meanwhile, back in Norseland, Loki maneuvers closer to Odin’s throne.

Kenneth Branagh, a Shakespearean quite at home with warring dynasties and high-flown dialogue, directs the piece with agile intelligence. When spectacle is called for, Branagh pulls out all the stops. The Asgard’s golden towers make oil emirates’ skyscrapers look like Tinkertoys. There’s a great new movie monster in The Destroyer, a giant, flame-throwing suit of armor. The battle scenes — it’s hammer time — surpass the thunderous war sequences in Branagh’s film of “Henry V.”

The film’s dazzle is in the details, however. Every character is rounded and shaded, every scene is performed to the smallest nuance. Hiddelston is charismatic and persuasive as the nominal villain, scarcely more flawed than his brother. Loki is no megalomaniac but a creature of misguided, deeply human motives. Hemsworth and Portman are fine separately and delightful together, bringing a light touch to their flirtation. Even beneath layers of costuming and makeup Idris Elba exudes watchful gravitas as Asgard’s gatekeeper, and Colm Feore is a fittingly cool adversary as the Frost Giants’ king.

“Thor” bridges the gap between high culture and low, between fanboys and mass moviegoers.

Film focus

WHAT: “Thor”

RATED: PG-13 for sequences of intense sci-fi action and violence

RATING: 31/2 stars

Chris Hemsworth, left, and Anthony Hopkins appear in a scene from the film “Thor.”