If you consort with Windows users you may want to avoid unwittingly passing on PC nasties. Otherwise, the current dangers are mostly social trickery and those irritating nuisance-ware apps headed up by MacKeeper and cronies.
For the former only heightened awareness and caution work; for the latter Malwarebytes (free mac version) is very effective. I use (free) Sophos Anti-Virus, although in recent years it has had almost nothing to act on thanks to ISP protection improvements
For full polar bear armour Malwarebytes (paid) is good. Be aware of subtle scams and avoid.
Apple update our defenses from time to time invisibly which is a real help, and their System Integrity Protocol (SIP) should not be turned off. Catalina locks down the macOS to make it more difficult to traduce.
Lionel Ogden 