Swiss artist Urs Fischer's wax sculpture Francesco (2017), purchased for $1 million,  is a four-metre high portrait of Italian art curator Francesco Bonami.

It is also a giant candle that will be lit every weekday and will melt, in public, over the next six months. People can revisit the gallery during that time and watch the process of melting and its ongoing effects. Each night the flame is extinguished.

Other wicks are contained within the work so the melting can be controlled. When the disintegration of Francesco is complete it will be sent to Zurich to be recast from its mould and returned.  When it is back in the gallery the process will begin again.

The gallery's director, Nick Mitzevich, lit Francesco and it didn't take long for wax to start dripping.

"This sculpture shows us that art in the 21st century shifts, it is not static, it is alive and always changing, reflecting the world in which we live," he said.

"It is the opposite of Michelangelo's David because it is wax, not marble, and will disintegrate as it burns to the ground."

The figure is holding a mobile phone, representing the modern world's obsession with the device.

The portrait sculpture is on top of a wax and metal model of a refrigerator, which will not melt. Its partly open door reveals wax replicas of fruit and vegetables, which when refrigerated in real life are preserved, but for a finite amount of time.

Senior curator of contemporary art Jakyln Babington said Fischer was one of the most important contemporary artists who in recent years had created similar wax portraits that would be melted and recast.

Francesco, she said, represented a constant cycle of destruction and renewal.

"It rises again like a phoenix."

Francesco will be lit from Monday to Friday at the National Gallery of Australia until August 23, 2019 and on display until August 25.  A timelapse video of its melting will be installed soon at nga.gov.au.