Why do we wear what we wear?

Force of habit, catwalk trends or high-street advertising? Perhaps our mode of dress has emotional meaning – a resonance with our past, or an aspiration of what we wish our present would be.

Cinema, though you might not always realise it, has probably had an influence too. Iconic characters create classic images, seared onto our brains. Marilyn Monroe in the white halter-neck dress, Audrey Hepburn in a black shift dress and pearls, James Dean in that leather jacket – their styles, created and imagined by Hollywood costume designers, have become a major part of our fashion lexicon.

The relationship between film, costume and clothes is about desire, about wanting to be another person. "We fall in love with the idea and we want to get close, and what can we do to get close? We can go to the high street and buy a leather jacket," says Professor Deborah Nadoolman Landis, costume designer and editor of Hollywood Costume, which has been published to go alongside an exhibition of the same name at the V&A Museum in London.

We've all done it, whether that's donning a stetson-inspired hat to be more like our favourite cowboy at the age of eight, or buying a copy of that beautiful yellow evening dress because Kate Hudson looked so great in it.

But what makes a film costume beg to be copied? For Landis, who has worked as a costume designer on Raiders of the Lost Ark in the Indiana Jones franchise and who was Oscar-nominated for her work in Coming to America, costume and character can never be separated.

"You can't take the costume out of the story," she says. But some of the most famous costumes – think Indiana Jones' leather jacket or even Charlie Chaplin's hat – are, when you analyse them, fairly ordinary garments: the kind of thing you could pick up on the high street.

"The clothes may not be that special because they're designed for narrative context and for visual context," says Landis. But there's no denying that some film costumes make that leap from ordinary to extraordinary – the kind of extraordinary that we want to wear in our droves.

For British costume designer Vin Burnham, who runs The Little Costume Shop and has worked on films such as Labyrinth, that extraordinary comes from having the "perfect combination".

She says: "Grace Kelly, when you look at everything she wore, she gave everything an atmosphere and a very special feeling. The garment could have been something fairly simple or ordinary but the way her costume designers and stylists did her stuff, they got it exactly right. So it was a combination of her and the stylist and the location and the lighting."

Burnham believes costumes such as Marilyn Monroe's white dress in The Seven Year Itch and Judy Garland's blue-and-white gingham outfit in The Wizard of Oz are made iconic through the actor and the fantasy of film.

"The Marilyn Monroe dress, it's not particularly remarkable, it just happened to be perfect for her," says Burnham.

"It was the right look for her and it was the way it was photographed. If you put it on a hanger you wouldn't look at it twice, but on Marilyn Monroe, with the way she wears it and the direction and the photography, that's why it's part of a bigger picture.

"When you think of Dorothy, it's a pretty dull outfit but you have to think of all the factors that make it iconic – it's not just three metres of gingham and a few metres of Broderie Anglaise – it's Judy Garland, it's everything that makes The Wizard of Oz The Wizard of Oz."

According to Burnham and Professor Landis our love of iconic costumes stems from our desire to be someone else.

It would seem that when our own life gets a little tedious we find it fun to become another character – a glamorous siren. But Burnham, who recently created one of Lady Gaga's stage outfits, The Living Dress, says: "Costume is made for performance, not everyday use."

For Professor Landis, who brought together the V&A's Hollywood Costume exhibition to show the role costume designers have in telling the story, copying the costumes she has created isn't the biggest compliment you could give her. In fact she'd rather you didn't notice her creations at all. "It [costume designing] is a profession that if you're doing the job right you're invisible, not only are you invisible but your clothes are as well," she explains. "We must leave no fingerprints. Fashion and costume design are completely different disciplines."

Different perhaps, but with so many beautiful clothes on the silver screen it's little wonder we get tempted to give them a whirl every now and again. As Professor Landis said, people "want to be in the movie, they want to be the star in that movie." The star in the beautiful dress.