Ello Ev'ry one!
@Malia it strongly depends on what OS your currently running.
If your running windows 10, windows defender has worked fine for me for years. just dont ignore it when it tells you something is off until you have researched it and KNOW that it is not infected. but then thats every antivirus weak point. uneducated exceptions making.
if using older than windows 10, (windows 8 or 7) please upgrade to windows 10. its free still you just have to know how.
(Disclaimer: this only works if you have an activated copy of windows 7 or 8.1 installed already and will not work if using a trial license or an unactivated copy or an older version.
download media creation tool from their website, create iso file or USB installer, open the finished media like any other folder and run setup.exe, manually change the updates options to the equivilent of "dont install now", and dont change the option to keep everything, run updates as soon as you get back to your desktop in both the windows store and the windows updates section)
if you are incapable of performing the above for one reason or another or simply do not want to do the sane thing and keep updated, i personally prefer bitdefender antifirus free. its light, small, and very effective in my personal experience, couple that with malwarebytes manual scans once a week and your security settings are shaping up nicely.
if your using MacOS, i still recomend bit defender. (yes macs get viruses too, and the MacOS viruses get much worse way quicker when you encounter them) unfortunately bitdefender for macOS is not free. you will need to pay but its not a crazy amount. like $60 per year. thats the same price as 1 year of Microsoft 365 personal. (i also highly recomend. i didnt always agree with myself there until i tried it and its been the best thing ive ever done. if you disagree, you are not a normal use case and/or have not done enough research and you need to try the 1 month free trial if you have not already done so)
back to topic, TL,DR :
use built in windows defender if using windows 10, if not, get it, see instructions above, or use bitdefender antivirus free and malwarebytes free. if using MacOS buy bitdefender or take your chances with another solution. I also revealed that Im a Windows 10 and Microsoft 365 fan.