Difficult to answer without knowing your exact use case. I'll give you the generic answer:
1) If your current OS and email client are up to date, then NO. You cannot endanger your system just by opening an email. As you mentioned, accidentally clicking on a link, button or image ( sometimes hidden as text ) may infect your OS.
2) Otherwise YES.
Back in the day, Outlook would run inline JS just by opening the email, this is no longer true. We now have webmail, many webmail solutions, it would seem that most block JS by default, but I can by no means speak to ALL versions of webmail available.
NOTE: a virus is a self replicating application, some do harm, some collect data, some use resources. By all definitions of an electronic virus a mac or linux system is safe from propagating malicious code, hence safe from viruses. This DOES NOT mean that you cannot damage or destroy your UNIX based system by clicking on something, it just means that your system will not automatically forward it through the local network and automatically damage other like systems. If you own a mac, you can still click and agree and enter your admin password and finally agree to destroy your system or hand it over to someone else.