Originally, Ant-Man was the superhero alter ego of biochemist Hank Pym, who invented a substance that allowed him to change size. He first appeared in the comic book Tales to Astonish#27 (which is cheekily referenced in the film) in 1962 and over the years has been the alter ego of several men.
While the character’s human alias has changed over the years, he has always been connected to the Avengers. Over the years, reformed thief Scott Lang and low-level Shield agents Chris McCarthy and Eric O’Grady have also taken on the mantle in the comic books.
Lang made a first appearance as comic book Ant-Man in 1979, the same year that the character made his live-action debut on Saturday Night Live in the sketch Superhero Party. For SNL he was portrayed by Barrett Morris, who has a cameo in the film as a cab driver.
In the film, Pym is played by Michael Douglas and does indeed create the shrinking process, but as we already know, unlike in the comic books, Pym does not create Ultron.
Anyway, Lang is played by Paul Rudd in the film and he will also star in Captain America: Civil War– though you have to wonder how closely the makers will stick to the comic books. Ant-Man is at one point killed by the Scarlet Witch, returned to life at a later point and then killed again in the Avengers Disassemble storyline, retconned and yes, the hits just keep on coming. Not for nothing is he known as one of the Marvel superheroes with the worst luck.
As Ant-Man, Lang in the comic books can shrink to half-an-inch when he dons the costume and communicate telepathically with insects and control them with his helmet. Plus, he can punch with as much force as a normal-sized human when shrunk and his helmet helps him to amplify his voice so regular people can hear him.