To not spoiler the movie for everyone is the summary quite short, but important characters to mention are also Loki (Tom Hiddleston), Thors brother; Thor's four companions the Warriors Three (Hogun, Volstagg and Fandral) and the Lady Sif (Jaimie Alexander).

The movie starts straight away, showing scientist Jane Foster (Natalie Portman), her mentor Erik Selvig (Stellan Skarsgård) and her assistant Darcy Lewis (Kat Dennings) investigating a mysterious weather phenomen/wormhole in the New Mexico desert.

There, they discover Thor (Chris Hemsworth) who was just stripped of his powers and exiled to Midgard (Earth) by Odin (Anthony Hopkins). Jane hits him right away with her truck and knocks the still confused Thor over. Her taser-trigger-happy assistant then finishes the job of knocking out the Norse God of Thunder.

A flashback is shown where we are able to watch how it came that binnen less than a day Thor went from the coronation ceremony, that should have made him king of Asgard (the Realm of the Norse Gods) to being banished by his own father.

It is now Thor job to prove that he is worthy of his title and powers.

(....)

The movie is a mix of the Norse Mythology and the Marvel Comics, the actors were well chosen for their roles and the special effects are a sight to behold.

(But you don't need any knowledge of the Mythology and/or the Comics to understand the movie, as it is mostly self explained.)

The DVD/Blue Ray contains deleted scenes which are a great addition to better understand the characterss and/or the relationships between this characters.

On a special Note:
The movie Avengers will contain characters from this movie, as well as Captain America, Tony Stark alias Iron Man, Hulk and other famous Marvel characters.