The Legion of Doom was in its heyday the premier supervillain team, opposing the Justice League, or depending on the universe, the Superfriends. The leader (and supposed founder) of each universal incarnation of the team is Lex Luthor.
In an upcoming issue of the Teen Titans, Superboy-Prime returns and forms a new Legion of Doom consisting of Sun Girl, Headcase, the newly resurrected Inertia and Indigo, Persuader from the Terror Titans, and Zookeeper.
Major Story Arcs
A version of the Legion of Doom first appeared in mainstream continuity by Brainwave Jr., during his time as a villain. This Legion of Doom consisted of Houngan, Killer Frost, the Madmen, Major Force, and a robotic Gorilla Grodd. The team confronted Captain Atom's Extreme Justice team and were defeated.
Also, in Alex Ross' series Justice, a form of the Legion appears. The supervillains around the world begin having shared nightmares of the destruction of the world. Believing that their ego and confidence is paving the way for their dreams of nuclear armageddon to become reality, the supervillains band together to defeat the Justice League of America and protect humanity in their own twisted way. Some of the villains start solving some of the world's greatest concerns, like hunger, which starts fooling the public into believing the heroes are a threat to society. After attempting to wipe out the heroes, Brainiac plans to turn Earth's inhabitants into robots using Mr. Mind-based mechanical worms. However, the heroes team together and prevent both the nuclear holocaust and defeat the villains.
The Legion of Doom is the only real Super-Team that's ever opposes the Superfriends, in the "Challenge of the Superfriends" TV show, which is lead by Lex Luthor, and is maned by all of the Justice League's primary villains, such as Gorilla Grodd, Brainiac, Sinestro, Bizarro, Toyman, Riddler, Scarecrow, Cheetah, Black Manta, Captain Cold, Solomon Grundy and Giganta. And at the End of every episode, The Superfriends always stop them but never bothering sending them to jail, so they retreat back to their swamp base that Looks like a Cross Between Darth Vader and Black Manta's helmet.
They have made constant appearances in the Superfriends cartoon, with thirteen villains opposing the Superfriends. However, some of them were rarely used and others were abused in turn. In each episode they develop a somewhat evil plan (being a kid show in its era meant little true supervillainy was allowed) and at the end of each episode the Superfriends defeated the plan. None of the members of the Legion are ever punished, as they always find a way to escape back to their base.
Also, The Legion of Doom has been referenced in an episode of Family Guy, and Solomon Grundy in particular has been parodied, when Lois comments some of her actions were taken on the belief the Legion was about to attack Quahog. Lex Luthor, observing the broadcast, wonders how could Lois know about the attack, and Grundy shyly confesses he "had dropped that one".
Justice League Unlimited
Later an updated version of the Legion appears in Justice League Unlimited. The roster of this version is much larger, holding over a hundred members of different supervillains. Its members treated that version much like a a supervillain union, whose leaders, Gorilla Grodd and Lex Luthor, lent members and offered support in different types of heists and criminal activities in exchange for a cut of the profits or even augmentation of powers in exchange for a hefty fee. Originally, Grodd led the Legion, and inducted Luthor as a normal member. However, Luthor rebelled and shot Grodd when it was revealed his master plan had been to transform humanity into apes all along. Not too fond of the idea, most of the Legion accepted the shift in leadership unquestioningly and allowed Luthor to use the Legion for his own plans. Later, during a phase when Lex Luthor was accidentally mind swapped with the Flash, Doctor Polaris tried to mount a similar coup against Luthor, but he did not count upon Luthor's plans-when he'd upgraded most of the Legion, he'd installed fail-safes in provision of such an eventuality, and Luthor remained leading the Legion.
In its final adventure, Luthor converted the Hall of Doom into a starship with the intent of recovering the last Brainiac pieces so he could again merge with the superintelligent android and recover his godlike form. Another riot broke out when Tala released Grodd to recover the leadership mantle, and the Legion was split into the side that followed Luthor, and the side that preferred Grodd altogether. Grodd was defeated and the dissenters frozen by Killer Frost, earning her a place at Luthor's side. Despite warnings by Metron of the New Gods, Luthor used Tala as a magical conduit to force Brainiac's rebirth. Instead, this brought Darkseid of Apokolips back. He destroyed the Hall and only the energy fields maintained by Sinestro and Star Sapphire saved the Legion until Lightray of the New Gods reached them, and Evil Star stole his Mother Box, enabling the Legion to return to Earth to warn the Justice League.
The Legion remnants fought valiantly against Apokoliptian forces, and as a sign of goodwill, Batman granted the surviving members five minutes of head start before the League gave pursuit.