Spam mails are having malicious embedded contents in it , by double clicking in them malware could be installed in the system an article to be read : Safety tips for handling email attachments and content downloaded from the Internet - Apple Support
And junk mails are if mail treats incoming mails as junk it moves into the junk mail box & genuine mails are received in inbox .
It is not a a question whether you make a separate folder for junk mails & spam mails . you have to stop mainly spam mails that could be malicious .
I had faced an issue in some web mail services , so I called their Toll free number they send me a link I signed with mail id & password , some steps were to be followed my mail id was deactivated immediately .
The support advisor that was on the call gave an information don't be tempted to sign in till 90 days, your mail id will be permanently deleted from the server and to be very honest it was deleted from the server .
Note : Share your mail id to trusted sources only .