Ground staff were forced to put the light covers on the MCG wicket an hour before play, with light rain falling and the 10am toss pushed back.
The drizzle came as Australian team debutant Scott Boland was presented his baggy green cap by injured quick Josh Hazlewood, with COVID-19 restrictions keeping the honour in-house.
Boland will become the fourth Indigenous Australian to play Test cricket and the first Victorian to make his Test debut on Boxing Day since current selector Tony Dodemaide in 1987.
Captain Pat Cummins is returning after he was forced to miss the second Test in Adelaide through a brush with the virus, while Mitchell Starc is the other quick retained.
Australia have a stranglehold on the series after winning the first two matches of the five-Test series convincingly.
A win or draw in Melbourne will mean they retain the Ashes.
By contrast, England are in disarray and have dropped four players for the Boxing Day Test.
Rory Burns, Stuart Broad, Ollie Pope and Chris Woakes were the casualties as England try to keep the series alive.
Bowlers Mark Wood and Jack Leach return to the England XI, while Zak Crawley and Jonny Bairstow will play their first Tests in this series.
Bairstow is expected to bat at No.5 for England, however Jos Buttler will still wear the wicketkeeping gloves despite his woes behind the stumps in Adelaide.
AUSTRALIA: David Warner, Marcus Harris, Marnus Labuschagne, Steve Smith, Travis Head, Cameron Green, Alex Carey, Mitchell Starc, Pat Cummins (capt), Nathan Lyon, Scott Boland.
ENGLAND: Haseeb Hameed, Zak Crawley, Dawid Malan, Joe Root (capt), Ben Stokes, Jonathan Bairstow, Jos Butler, Mark Wood, Ollie Robinson, Jack Leach, Jimmy Anderson.
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