The five founding members of the Avengers first banded together when Loki tricked the Hulk into destroying a railway line. So, the Hulk's friend, Rick Jones, radioed the Fantastic Four for help; however, Loki instead relayed the information to Thor to draw him out in the open so he could battle him. Unknown to Loki, Iron Man, Wasp, and Ant-Man (Hank Pym) also received the radio signal and arrived at the scene in an attempt to reason with the Hulk. Not falling for the trick, Thor confronted Loki and exposed his scheme to the others. The heroes then teamed-up and defeated Loki. Afterward, the group agreed they worked well together and wanted to formalize their team. The Wasp suggested the name "Avengers" and thus the legend was born. (Click on the highlighted names above to learn more about the characters. Note: Beware of the low-cut outfit worn by the female-version of Loki on his bio page.)
Iron Man provided the group with financing and high-tech equipment in his dual identity as rich industrialist Tony Stark, donating his Manhattan residence to serve as their headquarters--Avengers Mansion. Stark's butler, Edwin Jarvis, stayed on as the mansion's principal servant and chief of staff, becoming a valued friend, confidant, and adviser to the group. In addition, the team drew up a charter and by-laws to govern their operations. Also, the Avengers tried to receive A-1 security clearance from the federal government; however, they encountered resistance from the team's first National Security Council liaison, Special Agent Murch, and from the general public--mostly due to the uneasily feelings concerning the uncontrollable Hulk. Due to this, the Hulk ended up quitting the team. Fortunately for the Avengers, the team's image improved dramatically when they discovered (and recruited) the long-lost World War II hero, Captain America. A born leader, the living legend was given retroactive "founding member" status in place of the Hulk. Thanks largely to Cap's presence, the team eventually won its A-1 security status and rapidly became the most respected super-hero team of its generation. (To learn about the highlighted characters above, just click on their names.)
The team fought many battles against a variety of villains. Eventually, due to the high stress of being under constant attack (and for other personal reasons), most of the Avengers decided to take a leave-of-absence for a time. This left Captain America alone to lead a roster of unlikely new recruits, all former criminals: Hawkeye, Quicksilver, and Scarlet Witch. The new roster ("Cap's Kooky Quartet") proved their worth by defeating the Swordsman (Jacques Duquesne), Power Man, and Doctor Doom. (Click on the names above to learn more about the highlighted characters. Note: Beware of the revealing outfit worn by Scarlet Witch on Quicksilver, and her own, bio pages.)
Over the coming years, the Avengers membership proved very fluid. Thor, Iron Man, Hank Pym, and Wasp all returned for further tours of duty. Also, the four returning founders would all serve stints as team leader. New recruits during the team's early years included Hercules, the Black Panther, Vision, and the Black Knight. The alien hero Captain Mar-Vell became one of the team's staunchest allies during the cosmic Kree-Skrull War. The Black Widow even joined the team after years as an unofficial ally. (To learn about the highlighted characters and/or war above, just click on their names. Note: Beware of the form-fitting outfit worn by the Black Widow on her bio page.)
Eventually, the paranoid and combative federal agent Henry Peter Gyrich had become the team's new government liaison. He imposed reductions and modifications of the team's membership, during which time Falcon and Ms. Marvel joined; however, he was eventually reassigned. After a few more liaisons though, a humbled Gyrich later redeemed himself by serving admirably as the Avengers liaison to the United Nations. Meanwhile, the team continued to add new members such as such as Wonder Man, Tigra, and She-Hulk to the team. (Click on the highlighted names above to learn more about the characters. Note: Beware of the really revealing/form-fitting outfits worn by Ms. Marvel, Tigra, and She-Hulk on their bio pages.)
The group's expansion accelerated after they opened a second headquarters on the West Coast in Los Angeles. Hawkeye was sent their to be the new team's chairman. The West Coast Avengers consisted of famous heroes including War Machine, Thing, Mockingbird, and Moon Knight. Unfortunately, the West Coast expansion team gradually deteriorated under later leaders and was shut down after major losses of resources and personnel. Regardless, the original eastern roster continued to grow including heroes such as the Sub-Mariner, Mister Fantastic, Invisible Woman, Spider-Man, Thunderstrike, and Captain Britain. (To learn more about the the characters listed above, just click on their highlighted names.)
The group suffered setbacks, going through many changes of leadership and several changes of headquarters, losing various members and even disbanding more than once (most notably following a disastrous conflict with and Onslaught). In addition, there were some Avengers' allies who even refused membership into the Avengers. Some of the more notable ones are the Silver Surfer, Archangel, Iceman, Doc Samson, and Songbird. (To learn more about the characters above, just click on their highlighted names above.)
After a time when the Avengers was disbanded, a random gathering of heroes during a massive super-criminal prison (known as the Raft) breakout sparked the reformation of the "New Avengers." Iron Man and Captain America invited Spider-Man, Luke Cage, and Spider-Woman to join them as "New Avengers" and to capture the escaped criminals. Leading intelligence agency S.H.I.E.L.D. was reluctant to sanction a new Avengers team; however, Captain America reminded them that his "full champion license" status with the government gave him the authority to assemble any team he required for any given mission, so he required no approval from the authorities to reassemble the Avengers. Iron Man offered the top floors of his new Stark Tower skyscraper to serve as the team's high-tech headquarters (staffed again by ever-faithful Jarvis). (To learn more about the the characters listed above, just click on their highlighted names.)
On their many adventures to find runaway criminals, the New Avengers were able to capture Electro and track down Sauron to the Savage Land. In fact, the New Avengers teamed-up with Wolverine to oppose an illegal Vibranium mining operation run by Sauron's Savage Land Mutates. After the mission, the team recruited Wolverine--whose espionage background and ruthless attitude were seen as assets for the team. (Click on the highlighted characters, place, and/or item above to learn more about them.)
The Avengers also tracked down another Raft escapee, the Silver Samurai, to Japan where they ended up fighting against both Hydra and the Hand. Shortly afterward, Spider-Woman freed Madame Hydra. When the Avengers interrogated her, she revealed that long before the Avengers had recruited her, she had lost her powers. At that time, Hydra approached her with the chance to regain her abilities provided she become a double agent for them within S.H.I.E.L.D. When Nick Fury learned about this, he agreed to reinstate Spider-Woman into S.H.I.E.L.D. provided that she play a double agent for him. (Click on the highlighted characters, place, and/or item above to learn more about them.)
Soon after this, Professor X and Dr. Strange called a meeting with the Avengers and the X-Men to determine the fate of the Scarlet Witch. This, ultimately, is what triggered the events of M-Day where the world's mutant population was mostly de-powered. (Click on the highlighted characters, team, and/or event to learn more about them. Note: Beware of the revealing outfits worn by some on the M-Day bio page.)
Later, when the passage of the Superhuman Registration Act happened, the superhuman community was split. One side, led by Iron Man, approved and upheld the law that required the registration of superhumans. The other half was led by Captain America who rebelled against the new registration law. The superhuman "Civil War" made many Avengers take sides against one another. In the end, however, the Pro-registration side emerged victorious when Captain America was assassinated. (To learn about the Act above, just click on the highlighted name.)
More recently, after the Skrulls' Secret Invasion, Norman Osborn's Dark Reign, and the Siege on Asgard, the Avengers were reassembled, organized by the resurrected Captain America and backed by three splinter teams. Earth's mightiest heroes were whole again and ready to lead the universe into a new Age of Heroes. (Click on the highlighted names above to learn about the race, events, and character.)
To learn more about the Avengers, click on the following link, http://marvel.com/universe/Avengers.
In the movies, the Avengers seem to be connected with S.H.I.E.L.D. and Nick Fury. But, in the comics this in not the case. However, I'm sure the movie is going to be awesome anyway!