Robbie Williams and colourful frocks brighten Melbourne Cup under grey skies

Some early rain was not enough to dampen spirits ahead of the 166th running of the Melbourne Cup, with thousands to descend on Flemington in their finest to watch the race that stops a nation.

The wet start to the morning has been forecast to transform into a mild spring day with a top of 17 degrees Celsius as the big event gets underway, and builds up to the 3pm (AEDT) running of the cup.

Victoria Racing Club chief executive Kylie Rogers said the Cup was a key date in the city's calendar.

Ms Rogers said the fact that 60 per cent of general admission ticket holders across the carnival were aged under 35 showed its appeal.

"It's really important for sports administrators to be offering more than just the sport at these carnivals," she said.

"The way we're meshing fashion, great food and wine, terrific music acts — we've got Robbie Williams playing today, 75 minutes of Robbie Williams — amongst our racing … there really is something for everyone.

"Our attendances are up, our ratings are up, all our key metrics are up and it's feeling really good."

When he spoke to media ahead of Cup Day, Williams referred to Melbourne as "kind of my spiritual home".

"Obviously this is an event that is ingrained in your hearts and the way that people talk about it is with reverence," he said.

"I'm taking this very seriously. These are my mates."

He said he was backing horse number 24, Shockletz, after initially mishearing its name as "chocolates".

Farrier of almost 30 years, John Bunting, spoke to ABC 774 Melbourne about working with 19 horses taking part in the carnival this year.

He said racing rules around horse shoes, including that each individual shoe must weigh less than 150 grams, were in place to protect the safety of both jockeys and the horses.

Mr Bunting said most horses did not mind the process of having their hooves attended to by a farrier.

"They certainly feel our energy, so if we stay nice and relaxed, 99 per cent of them are fine with it," he said.

"I think a lot of them actually enjoy it, find it a little bit relaxing. It gives them a nice stretch."