MalwareBytes is the most-recommended third-party malware detector. But no senior contributors here advocate running it full time. It should NOT be in the list of launch agents or launch daemons. Run it on demand ONLY.
The thing is, MacOS completely changed how you should think about malware. Applications are all sand-boxed with a list of the resources they require, and they cannot ask for anything outside their sandbox without crashing.
From MacOS 11 Big Sur onward, the system is on a Separate, crypto-locked System Volume, which is not writeable using ordinary means. Any unauthorized differences that appear to the crypto-locked volume are quickly detected and you are alerted.
So you could store just about every malware known to mankind on your Mac, and your Mac would not get infected spontaneously. Scanning for virus-like patterns might make you feel a little better now, but it is outdated nonsense.
Nothing can become Executable Unless/Until you supply your Admin password to "make it so".