Is the sender someone you know and trust?
If so, you very likely have nothing to worry about on iPad. Over 99% of mobile malware is android. Desktop malware is laregly Windows focused, but I don't know the % share, so you'd be more at risk if you opened it on your PC. If you decide to open it, you'd be very unwise to allow it any access it requests like Contacts or Safari, or dog forbid, allow it to install anything. Given the closed eco system on a non-jailbroken iPad you should be totally fine. The system is built with security in mind from the ground up, not as an after thought.
General good practice still stands. If the sender is no one you've ever heard of and is neither a mail you expect or a response to an email you've sent, I'd just bin it and empty the trash. If it's from someone important they'll re-attempt or contact you another way. Even if you do read the mail in iOS then, as above, you'd be extremely unlucky to be vulnerable to the <1%.
It goes without saying if it's an untrusted or unknown sender, never open any kind of attachment or view any movie or click any link, never reply, head straight to trash and then put the bins out.
If your iPad is jailbroken, good luck, it could be anything