back in the old days, I used to use Avast, as it was considered the best of the free ones. Nowadays, I hear Avast is basically malware itself, so I wouldn't recommend using it. If you are using Windows 10, the one built in is probably good enough for everyday use. The main way you would get infected would be installing/running shady software. Don't download cracked/pirated software is the best way to avoid malware. Also, use an blockader. Drive-by malware ads are the main other way that malware spreads these days, and that is incredibly easy to defeat.
If you don't think the built in Windows anti-virus is good enough, you can try uploading downloads to virustotal.https://www.virustotal.com/gui/
It scans the upload across dozens of different anti-viruses.>>368