Should I check on malwares or viruses?

I know this sounds like a silly question, but my old Macbook was affected by malwares once and it reduced the performance honestly.

Looking back at my considerable numbers of encounter with ads saying "viruses" or "malwares", I see no reason to not be worried about my own OS health.

So, should I run malwarebytes again? (or any other checker apps, including malwares remover if I find one, would someone please recommend me one? and should I be worried about these free service sites that...

Should I check on malwares or viruses?