Gajeel is an tall and intimidating muscular young man around the age of Natsu Dragneel. His hair is a heavy metal, long, black hair and his eyes are small and red, with crimson irises and slitted dark pupils; he is normally seen glaring. He also has three scars on his right arm. His Fairy Tail tattoo is located on his left arm, just below his shoulder and it's black. He usually wears a wing-like sleeve on his right arm (right above his Phantom Lord tattoo) and various body piercings, usually in sets of three or five. His usual outfit consists of a shabby black tunic (that exposes his muscled biceps) with studded edges, studded wristbands, and studded boots (somewhat resembling Punk), white pants and a pair of brown gloves.
He doesn't seem to care at all about Fairy Tail, and seems to think that Phantom Lord is a stronger and more worthwhile guild. Gajeel bears his Phantom Lord symbol marked at the top off his right shoulder (note the same place were Natsu has his Fairy Tail emblem). When he was first introduced, he was depicted as cold and apathetic, and not at all above injuring his allies if they irritate him at even the slightest, as seen when he iron-clubbed a fellow Phantom Lord Mage who was praising his abilities, all because the latter was disturbing his metallic meal at the time. But at the same time, he appears completely dedicated to whatever guild he is affiliated with. In fact, he ignited the Fairy Tail-Phantom Lord Guild War (under Jose Porla's orders) mainly because, as long time-rivals, he believed that the Fairy Tail Mages were enemies, and as a Phantom Lord Mage, Gajeel sees it as an obligation to "protect" his own guild, even if it meant starting an unprovoked attack against Fairy Tail. Upon his recruitment to Fairy tail, this sense of comradeship did not change in the slightest; he even went as far as reprimanding Laxus (whom he admits to be a more powerful mage than he is) for attempting to kill Natsu with his lightning, when they are supposed to be allies.
As the strongest member of Phantom Lord under Master Jose, Gajeel's strength is immense. With his strength, Gajeel single-handedly defeated Shadow Gear, the "back-bone" team of Fairy Tail. His overall speed and reflexes are also impressive, being able to intercept attacks like Laxus' magical bolts and reaching Levy in time to save her from a double-team ambush of two Grimoire Heart Mages. His strength alone was also able to nearly destroy the first Fairy Tail guild building, and he nearly defeated an S-Class level mage (albeit not recognized as such at the time), "Salamander" Natsu, in combat. Like Natsu, Gajeel was taught by a dragon to manipulate a particular element into his fighting style. In Gajeel's case, the dragon Metalicana taught Gajeel how to use Iron Dragon Slayer magic. His skill in hand-to-hand combat rivals Natsu's, and with the support of his iron scales, he easily shifted the tide of battle into his favor for the majority of their fight. Even without his Dragon Slayer abilities, Gajeel has consistently proven himself to be one of the more resilient characters in the series: when he was confronted by team Shadow Gear after joining Fairy Tail, he was able to shrug off the combined attacks from Jet and Droy without retaliation and, in the the anime, only resorted to finally summoning his metal scales to increase his defense when Laxus tried to attack Levy. During the Edolas Arc, Gajeel used his metal scales to fight Faust's mechanical dragon , where he absorbed extremely powerful blows with little trouble.
Gajeel also seems to know how to use his magic to revert those who have been turned into lacrima back to normal, most likely after being taught to him by Mystogan.
Iron Dragon Slayer ( Tetsu Metsuryū Mahō): Like Natsu, Gajeel knows "Dragon Slayer" magic, which he learned from the dragon, Metalicana. However, his Dragon Slayer magic deals with metal instead of fire. Just as Natsu eats fire to regain his strength, so can Gajeel eat metal to regain his own. His teeth and jaw muscles are apparently powerful enough to gnaw through solid metal with ease, and can devour even the magic-canceling metal of the Dorma Anim. Gajeel's magic seems to deal with producing multi-sized iron rods as well as changing parts of his body into steel. Most of his attacks involve transforming his arm's into hard-as-steel weapons, which he can do at will.