Film robots are normally mean machines, but in the latest animated movie, WALL-E, the hero shows his mettle and saves the day.

Steve Pratt pushes a few buttons.

SHE’S sleek and sexy. She’s young and beautiful. But she’s different from other girls. The clue is in the name – False Maria. A human face has been imposed on an android, who’s taken as human in the future world of Fritz Lang’s 1927 science fiction film, Metropolis.

Maria’s the first in a long production line of man-made machines that have clanked across the cinema screen. Robots are all the rage with film-makers. They come in all shapes and sizes. Some are good, most are bad. Some look like deformed tin cans, others are the spitting image of us.

The line between human and machine is blurred in False Maria, the big screen’s first close encounter with mean machines. Robots, droids or replicants (if we’re in Ridley Scott’s futuristic world of Blade Runner) aren’t flesh and blood, but often pass themselves off as human.

Consider Jude Law’s Gigolo Joe, one of the best-looking robots ever to grace the screen in Steven Spielberg’s AI: Artificial Intelligence. “Once you’ve had a robot lover, you’ll never want a real man again,” he says.

A Japanese roboticist coined the term “the uncanny valley” to explain why robots with human characteristics or those who look like humans appeal to us, while those that look just like a talking washing machine fail to stir our emotions.

What would he make then of WALL-E, endearing robot star of the new animated feature from Pixar, makers of Toy Story and Finding Nemo? WALL-E is unmistakably not human and, while his conversation is limited, he has a big heart. His lonely existence as the last “living” thing left on a desolate planet Earth stirs our emotions.

His love of showtunes, notably Put On Your Sunday Best from Hello Dolly, might lead some to suspect he’s the cinema’s first gay robot, but then he goes and falls for a sleek female machine called EVE in a love story rivalling anything Shakespeare wrote about starcrossed lovers.

He belongs to the gallery of cute robots in the mould of Short Circuit’s Number 5, who bears a passing resemblance to WALL-E, and Huey, Dewey and Louis from Douglas Trumbull’s ecologocial space story, Silent Running.

Screen robots have progressed far since Metropolis and False Maria being used by the powers- that-be to combat rebelling workers. She started a trend for machines to cause trouble.

Metallic heroes like WALL-E are rare. Most robots destroy people and property. Terminator is such a beast, although later models of Arnold Schwarzenegger’s monosyllabic robot were programmed to protect not destroy.

That’s left to the T-1000 model in Terminator 2, whose makers took advantage of technological developments that enabled them to show him morphing into the shape of anyone he touches. He’s as deadly as the killer robot dolls who try to peck Jane Fonda’s space woman to death in Barbarella, or the androids who take against humans in I, Robot.

You’d expect Robocop to maintain law and order but this half-man, half-machine, cobbled together after Peter Weller’s policeman is gunned down, prefers to shoot first and ask questions later.

For pure evil it’s hard to top Proteus in Demon Seed. The robot ends up raping a scientist’s wife (played by Julie Christie). Android Hector gets randy in the Martin Amis-scripted Saturn 3. The object of his affection is a pre-Charlie’s Angels Farrah Fawcett as the machine mirrors the feelings of his master (Harvey Keitel).

If they’re not bad, robots are expected to be funny. They provide the light relief, like Data in Star Trek: Generations or the most famous robots of all, R2D2 and his golden companion C- 3PO in the Star Wars movies .

One sounded like an English butler, the other communicated in beeps and burps. They were allowed to lend the hero a mechanical hand and gave George Lucas’s space adventure flashes of humour in their verbal exchanges. We expect robots to be bright and Robbie in Forbidden Planet can speak 187 languages, has a dry sense of humour and is revered as “a triumph of cybernetics only one step removed from total humanity”.

When the machine looks human, you can expect trouble although they have their uses. The Stepford Wives cook, clean and do whatever their husbands command. They don’t look bad in a glossy American housewife way, either. In the case of Transformers, you can’t even get in your car and drive away from the enemy – because your vehicle might turn into a robot fighting machine.

With the success of WALL-E, our screen relationship with robots is veering more towards love than hate. But watch out, the Terminator is returning, minus Schwarzenegger, but no doubt with an equally troublesome robot.

■ WALL-E (U) is now showing in cinemas