If you're going to be in Australia for an extended period of time, you will need to register for Medicare, otherwise you won't be covered if you have an accident or need to visit a GP or hospital.
Medicare automatically reimburses the majority of your medical costs to your bank account after you've paid it. This means if you need any medical care you only a small percentage of the cost. So it's definitely worth doing, as it's free to register.
You will need an Australian bank account, passport and proof of your visa status when you apply. You can print off the registration form and take it in to any Medicare centre. It only took a few minutes for mine to be processed and then they posted my Medicare card to me within a week.