Jim wants to know if Windows Defender is sufficient to protect his Windows machine against malware. Leo says yes and now. You are your own last line of defense and your online behavior can undo the hard work Defender does to protect you. Don't click on links in an email. Only get your software from original vendors. Keep DEFENDER and Windows 10 up to date.
Defender is as good as any other antivirus, but safer since it's designed specifically for Windows.