Hey there!
Most Australian graduate medical schools accept any type of undergraduate degree -- including commerce. You'll need a competitive GPA/WAM, a competitive score in the
GAMSAT, and after that, your interview score.
I'll just make some notes about Victorian medical schools. If you apply for UniMelb Med, you'll need 2nd-year units in Anatomy, Biochem, and Physiology, details of which can be found
here. I'm not entirely sure if this can be done via breadth, so hopefully someone else can answer here. If you apply for Monash Med, they
only accept degrees from Monash. They have 50 reserved spots for the top-performers in Biomedical Science. Otherwise you'll need a degree in Science (if you've completed some of the units listed
here), Physio, or Pharmacy. Commerce won't qualify you here, although a double-degree w/ science will. Deakin is chill, your commerce degree would be fine there.
Also, UMAT doesn't matter at all for grad-entry -- that's just for undergrad entry