Are Malwarebytes and Antivirus software necessary for a new MacBook Air?

MalwareBytes isn't really AV software. Its main purpose is to locate and remove known adware and malware you've already installed.

All other AV software is useless. Completely. There are no viruses for any Apple device, which is malware that self replicates. There are plenty of Trojans, which is malware the user must install. It can't get there by itself. And AV software almost never makes any attempt to stop you from installing Trojans since it can't know what it is you're installing or launching until after the fact. And even then, they almost never flag it.

A browser is browser is a browser. None of them can be bypassed by crooks to put malware on your system. All attempts try to scare you into doing something you shouldn't. Like throwing out big, loud pages screaming your system has xxxx viruses installed! Bull. No one - literally - no one can tell what's on your computer through a browser.

To add to Kurt Lang's "right on" comments, if you follow the warnings and instructions in these two user tips: Effective defenses against malware and other threats - Apple Community and Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support.  and you do not click on any links in texts and emails that you don't know the sender you should be very safe.

I use Malwarebytes occasionally when my iMac shows strange popups or warning notifications. The free version is adequate for most users.

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc., which is handles nicely by Malwarebytes.

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

Also, unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, they provide false security from a privacy standpoint. 

... Do I need malwarebytes? and why?

The answer to that question is no, you don't need it. If you did then Apple would have included it with every Mac they sell. They don't. In lieu of that, macOS incorporates multiple layers of defenses that intervene in attempts to install something potentially malicious.

If you were deceived into installing something you don't want, or need, then you deliberately bypassed those layers of defenses. It is a simple matter to remove what you installed without installing anything else. macOS already includes all the tools you need to do that (it's called the Finder).

A Mac would not be the useful tool that it is unless we could download and install things — even things no reasonable Mac user would want, or need. Do you want someone or some thing to make that decision for you?

And Do I need antivirus software on a mac?

The answer to that question is no, you don't need it, and your Mac won't work properly if you were to install anything like it. macOS already includes all the protections it needs to defend itself from viruses and malware.

CuriousAgain wrote:

I'm in the process of setting up a new 13" MacBook air M3 (my second mac) and attempting to learn a lot more this time. Do I need malwarebytes? and why? And Do I need antivirus software on a mac? Some people say no, others say yes, for google and browsers other than safari...

If you allow the Social Media platforms shape your opinion on the need for Third Party Software to protect the Apple Computer from Viruses and Malware, they have certainly steered you in the wrong direction

There are no known Windows-like Viruses in the wild that self replicate and affect macOS, because of the underling UNIX  Foundation and Permission Limitation. 

The Operating System resides in a Sealed and Read Only Volume that cannot be opened by the User nor by Third Party Applications.

Security. Built right in

Mac app security enhancements

 The Built in Security  is all that is required to protect the computer

Thanks to a long standing contributor @John Galt and refer to below links

Stop unwanted Notifications

Phony "tech support" / "ransomware" popups and web pages

CuriousAgain wrote:

Thanks for this input, both you and Kurt Lang. The "some people say..." I was referring to was NOT social media, rather two Apple Genius Bar people which is why I wanted to ask more people familiar with apple products. I also appreciate the links you provided.

You are welcome

As I was not physically present at the time you had a face to face conversation with the " Apple Genius Bar people "

It would be improper for me to make any comments specific to this conversations