The Inverse Law of Complexity to Power- "metal" is a very broad term, and all metals are very utilitarian, so even if what can be done with the metal is narrowly defined (shaping it, magnetizing it, moving it...), it's still capable of many things.
In modern series, Elemental Baggage isn't a problem for metal (if it's even in play at all), so while your enemies may be caught without water or dirt to use, you'll never have to worry as long as you're anywhere near civilization.
Also common in Digimon games is to have a "Machine" element.
Fist of the North Star has Boss Fang, who can turn his body into steel... not that this did him any good against Kenshiro.
One Piece has Mr. 1, who, after eating the Supa Supa [Dice Dice] Fruit, got a body literally Made of Steel as well as the ability to form bladed weapons on any part of his body.
Eustass Kidd to a lesser degree, who has the power of either Magnetism or Metalkinesis.
Captain 'Black Cage' Hina: Her DF lets her create iron shackles through various ways.
Fairy Tail has Gajeel Redfox (pictured above), who uses Iron Dragon Slayer magic. To clarify, this allows him to turn parts of his body into metal weapons (usually clubs or a sword), cover his entire body in metal scales (again, pictured above), and use a tornado of metal shrapnel as a Breath Weapon. He can also eat iron and metal to recover stamina.
Naruto: The Third Kazekage could create and manipulate iron sand using magnetism, which Sasori took advantage of after killing him and turning his corpse into a puppet.
His successor, The Fourth Kazekage can manipulate gold dust using magnetism (which is surprising since gold is not magnetic).
A minor character from the Cloud Village named Toroi had that same bloodline technique (which surprised a Sand Village ninja to find out it was found that far away) which he uses magnetize weapons, which magnetize other objects they hit (including people), making his attacks nearly impossible to avoid.
This is also the power of one of the filler villans from the Land of Vegetables arc. Hinata defeated him by breaking his "off" switch with Jyuuken, burying him in his own sand.
Musica and Reina of Rave Master are "silver claimers", who can both manipulate silver, though Reina has the slight advantage of being able to create silver out of thin air.
In one arc, the pair form an Enemy Mine against Ogre, who turns out to be a gold claimer.
In A Certain Scientific Railgun, the title character, whose main power is Shock and Awe, at one time manipulates iron sand into whips. And uses it to stick to walls... and to disarm people with guns... and to instantly form shields in front of herself... And of course the titular Railgun. Seems like this is closer to her main power, in the way she actually uses it. Or rather, the series make no distinction and her power is simply Electromagnetism.
Sailor Venus from Sailor Moon has power over metal, one of her weapons is a "Venus Love Me Chain" and she was able to escape the Amazon Trio's metal restraints rather easily. Her strongest attacks in the manga involve the use of her chain weapon and she uses a sword in the first story arc. She did use the chain for her attacks in the live-action series, being able to manipulate its length, and used a similar sword (though with different powers).
Caro Ru Lushe from Magical Girl Lyrical Nanoha StrikerS has the spell Wrought Iron Summonnote Rentetsu Shōkan that allows Caro to summon, transmute and control inorganic matter in nature. This includes Alchemic Chain, that is made of iron and not of magic like most other chains.
Magneto can not only affect magnetic forces and metals, but generally can also manipulate and shape non-magnetic metals just as easily.
Polaris had the same powers, resulting in decades worth of wrangling about whether or not she was Magneto's daughter (she was introduced as such but the very same storyline revealed it to be a hoax, and it's been just as back-and-forth ever since). Current continuity says she is; we'll see if it sticks.
Also, Magneto's clone Joseph.
Magneto takes it further than even manipulation of metals; electromagnetism is one of the four fundamental interactive forces of the universe (the others being gravity, strong nuclear force and weak nuclear force). Unlike many characters with similar powers, Magneto is well aware of this. At times, he's pulled off feats like locally negating gravity (causing killer Sentinal robots to be hurled into space by Earth's rotation), and he routinely uses his powers to create a forcefield around his body, which can even hold in oxygen (needless to say, neither metal nor magnetic) when he feels like spacewalking without a spacesuit.
So powerful is his full range of abilities, most adaptions of Magneto have to severely limit his powers down to the most basic form of metal manipulation, Not Quite Flight and electromagnetic shields. Any more and it risks becoming a Story Breaker Power.
In Ultimate Spider-Man, the end of the Clone Saga reveals that Ultimate Doc Ock's control of his arms was actually control over METAL. This leads to a much tougher fight than Spidey was anticipating, and one of his clones being Impaled with Extreme Prejudice right off the bat.
In The DCU, the original Doctor Polaris and his successor both had magnetic powers.
Milestone Comics' Static has basically the same powerset as Magneto, except visually based more on the electricity side of electromagnetism. He still largely uses it to move metal objects around, though.
In The Incredible Hulk 's third or so issue he faces off against an alien called Metal Master who promptly waltzes over Hulk. Hulk comes back for round two with a gun that Banner and Rick Jones have made, which the Metal Master can't control. Hulk promptly knocks him out because the gun was made of cardboard.
Metalcrafting is but one of the Elemental Powers available to furycrafters in Jim Butcher's Codex Alera. Metalcrafters tend to be the greatest swordsmen, since some of the metalcrafter skills include the ability to sense metal around you and act on that, as well as the ability to greatly increase your own endurance and pain tolerance (a famous duel between two metalcrafter lasted days). One character also becomes a Chrome Champion in the fifth book and another character does the same in the sixth. Metalcrafting also allows one to control their own emotions and shield them from having their emotions detected by watercrafters. Lastly, metalcrafting includes some degree of kinetic control over metal, but since only two very powerful crafters have been seen using it (Gaius Sextus and Invidia Aquitaine) it's probably a difficult technique.
All magic in the Mistborn series involves metal in some way, but the closest examples to this trope are the two Allomantic powers gained from iron and steel, which allow the user to attract (iron) or repel (steel) nearby pieces of metal. This power is not based on magnetism, and affects all metals except aluminum, which is allomantically neutral. There are three general types of metal-based magic:
Allomancy, which involves ingesting and "burning" metals to generate effects, ranging from the aforementioned pushing and pulling of metals to ehnacing physical abilities and senses to detecting or hiding other using allomancy. With certain rare metals like atium, one can see into one's opponents' future. Allomancy is also the power of the god Preservation.
Feruchemy, which allows for an Equivalent Exchange wherein the feruchemist takes something from themselves, be it physical strength, knowledge, speed, weight, or sensory ability and "stores" it in metal to draw upon it later.
Hemalurgy, an inherently destructive use of metal spikes to steal attributes from others and transfer it to another. It involves killing the "donor" with the spike to extract the attribute from them and then pounding it into the body of the "recipient. Doing both at the same time boosts the effect. Hemalurgy is also how koloss, kandra, and Inquisitors are created. Hemalurgy is the power of the god Ruin.
Metal also has one other inherent and very useful magical property: neither Preservation or Ruin can "see" it, as metal and the powers relating to metal look like brilliant, blinding lights to them. This is a critical component of the story, as Ruin can alter written words on anything except metal, and he does this to alter historical records and prophecies. Anything not etched into metal is untrustworthy; even knowledge stored in a feruchemist's metalminds can be altered, but writing on the metal itself cannot. Once this is apparent, the heros are able to keep Ruin from learning their plans by using messages etched in metal. However, Ruin is able to get around this by having his Inquisitors ambush the messengers and read the metal and transfer that information directly to him.
Daja Kisubo from Tamora Pierce's Circle of Magic series is an apprentice blacksmith with metal and fire manipulation.
Each Guardian has a unique Gift. Irena's is the ability to manipulate metal, and she supplies all of the Guardian angels with perfectly customized weapons. Her gift works even better in tandem with her ex-lover's Gift of fire.
The Rook: Joshua Eckhart can " ... manipulate metal. Under his touch, it becomes fluid, malleable; it assumes any shape he desires. It isn’t magnetism. He can’t attract or repel it. He sculpts it, gathering it up in great glistening handfuls and molding it into new shapes."
The Zombie Knight has its protagonist. The metal power is categorized under "materialization," which is described in-story as "the ability to create something from nothing." The power gradually develops in a variety of ways as the story progresses.
The Man Who Controlled Metal. The title kinda says it all. The title character, Alec, uses his ability to scare a mugger straight, by cutting into his throat with the mugger's own knife. While Alec just stands by and watches. Pretty hardcore.
In Enochian esoterism the solar angelic Prince Bornogo is associated with metal.
BIONICLE has Iron and Magnetism elements. There is a lot of overlap in their powers, but the main difference is that Toa of Iron can create metal from thin air, and Toa of Magnetism have to manipulate existing metal or just use magnetic energy.
Ace Lightning has Random Virus, a morally confused cyborg with limited control over metal.
Gold Wizards in Warhammer Fantasy are Imperial alchemist/wizards whose spellcasting specialises in modifying existing alloys and chemical components.
The advanced techniques available to Earth Aspect Ryuujin in the Exalted shard Burn Legend are all forms of this. They range from a stagger-inducing iron-enhanced bear hug to ripping the engine out of a car and kicking it into the guy trying a jump attack.
Pokémon has the Steel-type. Mons with this typing tend to be either powerful defenders (like Skarmory), potent tanks (like Metagross and in the lower tiers Aggron), or Lightning Bruisers (like Scizor, Lucario and Excadrill). Part of this is due to having the largest spread of elemental resistances in the game at 10 (formerly 11) and an immunity to Poison and Toxic statuses. It would be a good candidate for Infinity+1 Element itself, except that the few weaknesses it has - Ground and Fighting in particular - are very commonly found in the game and are downright ubiquitous on competitive teams. While Ground and Fighting are powerful attacking types on their own, it's safe to say a lot of their value comes from their ability to hit Steel-types hard. Most dual-typings with Steel tend to negate one or more of those weaknesses though. Moves of this type usually revolve around turning part of the Pokémon's body to metal and using it to attack (Steel Wing, Metal Claw, Iron Tail, etc).
Another problem the Steel typing faces is that it is resisted by Fire, Water, and Electric types while only being super-effective against Ice and Rock, which already have a number of weaknesses already, therefore, it isn't normally useful as an attacking type. They are however the only type besides Poison that is super-effective against Fairy-types.
As for Gym Leaders, we have Jasmine from Olivine City and Byron from Canalave City, who use Steel-type Pokémon.
Steven Stone as well, although his team is pretty evenly split between Steel and Rock/Ground types.
Arcana Heart has Fiona Mayfield, whose default Arcana is Orichalkos, the "all-knowing Mr. Dragon" who is also the Arcana of Metal. With him, she is able to create metal swords and shields out of thin air and attack with them.
Shirou too, in a strange way. His element is more specifically "swords."
Schwer-Muta from RosenkreuzStilette, a Mega-Man-esque doujin game, follows the same formula as Junk Man above.
Patchouli from Touhou has metal as one of the 7 elements she uses.
Suwako also has this as part of the her earth goddess powers.
Mordekaiser of League of Legends. His title is "The Master of Metal", though in this case it refers to both his ability to control metal and his ability to rock out.
K'thonya of Earthsong belongs to a race with the soulstone ability to manipulate metal. Essentially the only thing she can't do with it is turn one kind into another and create it out of thin air (though she can expand a relatively small piece of metal to many times its original size). Her species' hair has a high enough metal content to be subject to her power, and the use of this ability by other members of her race apparently inspired gorgon myths in Earth culture.
Perepis of the Global Guardians PBEM Universe can telekinetically manipulate metal, as can Ogun (who wears a suit of telekinetically manipulated "Powered Armor"). Mercury, a liquid-metal shapeshifter akin to the T-1000 can form his own body into various metallic shapes.
Warrick Kaine of The Descendants has the full suite of metal themed powers; controlling, sensing (apparently it's like taste) transmuting, and creating Instant Armor. Somehow, this also lets him summon sentient Combat Tentacles too.
Whateley Universe character Silver secretes mithril and can shape it into weapons too.