First appearance of the original X-Men comprising of Professor X, Cyclops, Marvel Girl, Iceman, Angel and Beast. First appearance of Magneto.
*A training session at Professor Xavier's school is halted by mental command from the professor, who tells his for students - Cyclops, Iceman, the Angel, and the Beast - that a fifth student has just arrived outside. As the boys leave to change out of their uniforms, Jean Grey enters, and the professor explains that he asked her there because she is a mutant with a power normal people do not possess. Then he introduces her to the other X-Men, so called for their extra powers, and nicknames her Marvel Girl.
To satisfy the boys' curiosity, she demonstrates her telekinetic powers. Then Xavier declares that he, too, is a mutant, and tells why he founded his special school. There are many mutants walking the Earth, he says, and some have evil motives. It is the X-Men's job to protect mankind from those "evil mutants."
Meanwhile, from a laboratory near the Cape Citadel missile base, a mutant named Magneto causes a rocket to plunge into the ocean as a demonstration of his magnetic power. Then, skywriting magnetically with airborne dust particles, he delivers an ultimatum to the base: surrender or else. The military refuse, so Magneto attacks the base in person, surrounding himself with an impenetrable magnetic field, and the soldiers cannot prevent him from taking over.
A radio bulletin alerts the professor, and he sends the X-Men in his mentally controlled jet to Cape Citadel. The military, who have been evicted from the base, give the X-Men fifteen minutes in which to get through the magnetic force field that has sealed off the installation. Following Professor X's mental commands, Cyclops eye-blasts the field, and the feedback causes Magneto to turn the field off. Magneto retaliate with five hunter missiles, but the X-Men easily evade them and attack Magneto directly. Magneto hurls metallic debris at the Angel and shoves a tank car filled with rocket fuel at the teammates, but the escape when Cyclops burrows underground with his eye-beam. When they emerged to counterattack, Magneto decides to give up and flies away, leaving a magnetic barrier behind to prevent the X-Men from following. Having earned the gratitude of the military, the X-Men return to their school in triumph. *Source:Official Marvel Index to the X-Men (Vol 1) #1