Good and useful information about Malware is on the Computer Club web site. A bit of searching on the internet for Malware is likely to provide days of reading. This site: AV-Test.org does good work. My opinion of av-test.org results… There are plenty of good choices for AntiVirus, including free options. This item about Avast vs Microsoft defender is “interesting”.
The past couple of years, Windows Defender has been adequate as an anti-virus tool in the home environment. In the Help Center we do see client computers with other flavors of Anti-Virus and firewalls. Most of the time we encourage the removal not-free anti-virus or firewall tools. Why? We prefer free. Windows Defender is free and it works.
The Help Center does use free versions of Malwarebytes, CCleaner and Superantispyware to “disinfect” a computer. These tools can be helpful on an infrequent basis. If these tools are enabled to run at system boot time, it is likely they will impact system boot performance.