User is a human being that has developed powers and abilities from a variety of causes, such as evolution, genetic experiments, enchantment, having powers bestowed upon them by other beings or sources, through birth, and training in order to obtain said powers. Also, thanks to the human side of their heritage (if the powers are genetically-based), they are able to use these abilities without becoming a monster (i.e. keeping their human physique, sanity, and humanity without it being altered from possible instability).
Depending on the amount of powers they possess, especially regarding resistance/immunity, etc, Metahumans can be much stronger and more powerful than regular Humans in the long run. For example, they could survive environments that would be otherwise dangerous to normal Humans, they can defeat threats that regular to peak Humans couldn't fight back, and can even handle occupations to a much better intuitive standard, as well as acquiring better skills that normal to peak Humans could never hope to reach.
By definition, the prefix Meta, simply means beyond, which also qualifies to Metahumans that they are Homo Sapiens that are beyond the limitations of their kind, which would make them the very staple of their derivative race that they stem from.
Homo Superiors can also be divided into two categories:
Metahumans of this category gain their powers via evolution, birth, genetic engineering, or exposed to radiation or biohazardous substances, like mutagens, or any other methods that involves genetic experimentation in that regard.
In one way or another, certain Homo Superiors that are of this classification will may have minor physical changes without their humanity being fully or almost slipped away, like their irises changing to any color like a fiery shade of red, yellow, purple, etc, retractable claws or spikes, fangs or sharp teeth, color of the skin being changed, among others. In fact, these kinds of Superhumans will be able to possess powers without their physiology being altered and lose their humanity as a result.
Non-Genetic Metahumans gain their powers whether they have abilities bestowed upon them by supernatural beings, enchantment, training to bestow powers like Telekinesis for example, being blessed or granted wishes to obtain powers, and among any other methods without any genetic tinkering. Unlike genetic-based Homo Superiors this category of Metahumans wouldn't have to be able to suffer mutations and instability of their Deoxyribonucleic Acid, which can be caused in certain ways. Just because Superhumans are of this category, doesn't necessarily mean they are any weaker than genetic-based Metahumans.
Alex Mann/Action Man (Action Man 2000) is a Metahuman who uses the AMP Factor to predict eventual outcomes, and alter them via choices of obstacles that he must use to prevent the happenings before they occur.
After being struck by lightning Templeton Storm/Tempest (Action Man 2000) has gained powers based on electricity.
Wolfgang Greenholtz/Professor Gangrene (Action Man 2000) is a scientist whose experiments accidentally turned him into a Superhuman.
Victor Fries/Mr. Freeze (DCAU) became a Metahuman after an accident left his body soaked in a freezing solution. The accident rendered him unable to survive outside of a sub-zero environment, but also slowed his aging process to the point where he is essentially immortal.
Matt Hagen/Clayface (DCAU) became a methuman after an over-exposure to the Renuyu formula mutated his entire cellular structure, turning him into shape shifting entity of a clay-like substance.
Leslie Willis/Livewire (DCAU) became a Metahuman after she was struck by a lightning bolt, causing her to become a Human of pure electrical energy.
Rudy Jones/Parasite (DCAU) became a metahuman after being covered in experimental chemicals, resulting in him becoming an energy-draining Human.
Dinah Lance/Black Canary (DCAU) is a Metahuman that can emit ultrasonic screaming, known as the Canary Cry.
Claire Selton/Volcana (DCAU) is a Metahuman who experienced her ability of pyrokinesis around her teenage years.
After being dosed with the mutagenic chemical known as Quantum Vapor, Virgil Hawkins/Static (DCAU) became a Metahuman with the ability to manipulate and control electromagnetic phenomena.
Much like Virgil after he was exposed to Quantum Vapor, Francis Stone/Hotstreak (DCAU) became a pyrokinetic, able to project powerful blasts of flames from his body.
After he was exposed to the Quantum Vapor, Ivan Evans/Ebon became a Metahuman with the power of a living shadow.
Derek Powers/Blight (DCAU) became a Metahuman after becoming infect by his own nerve gas combined with radiation exposure made his body entirely radioactive.
Major Glory (Dexter's Laboratory) is not only the supreme leader of the Justice Friends, but he's also a powerful Metahuman.
The Inhumans (Marvel Comics) are a race of genetically altered humans designed by the Kree.
James Howlett (Marvel Comics) later known as Logan and Wolverine.
Scott Summers' (Marvel Comics) optic blasts manifest for the first time.
Warren Worthington III (Marvel Comics) manifesting his wings during puberty.
Luna Maximoff (Marvel Comics) is a Mutant/Inhuman hybrid.
Wanda Maximoff (Marvel Comics) is a mutate with probability-based powers due to being being experimented on by the High Evolutionary as an infant.
Reed Richards (Marvel Comics) is an example of a mutate, someone who has gained their powers from a mutation through an external factor, in Reed's case cosmic radiation, rather than being born with those powers like a mutant due to lacking the X-Gene which mutants possess.
Jerry Montrose/Pyre (Rising Stars) is one of the Specials.
Pamela Isley better known as Poison Ivy (DC Comics) is a metahuman due to an accident that gave her powers and turned her insane
Various Characters (To Aru Majutsu no Index) have either science-based or magical influenced powers.
Quirk-Users (My Hero Academia) are humans - and occasionally animals - who are born with a specific superpower or "quirk". Within the entire earth, quirk-users make up over 80% of the world's population.
The Vinsmoke siblings (One Piece) are modified humans.
Ryūhō Tairen and Kazuma (s-CRY-ed) are known as Alters, individuals who are able to shape and reconstruct matter through mental focus and willpower.
Kai Kudō and his friends (E's Otherwise) are as Espers born with psychic powers.
Conduits (inFAMOUS) are humans with a special gene that can either be activated naturally or through scientific means, granting them unique powers.
Lena Oxton/Tracer became a Superhuman through an accident regarding the aircraft she's using with a teleportation matrix malfunctioning, giving her abilities associated with time, like Temporal Rewind, Temporal Healing, and Time Acceleration.