These days "Anti-Virus" and "Anti-Malware" is often the junk that you have to be wary of. The vast majority of these programs simply take advantage of user's worries, but do almost nothing when it comes to actually protecting them. Instead, the programs serve to:
1. Display advertisements.
2. Collect information/telemetry about you and your device which they then sell.
3. Pester you to upgrade the program to a non-free version, more expensive & unnecessary features, renew subscription, etc.
4. Present false-positives, or sometimes show you things that are real but not necessarily relevant or a threat, display them to you in a way that makes you believe the app is doing a great job and super important.
It's amazing how many computers and devices I clean up these days that aren't actually infected with anything, but ended up with several of these junk apps/programs on them that needed cleaning off. It's nice how much cleaner of an experience it is once the programs get removed.
Most phones and tablets give apps very limited access to the device itself. Apps are actually fairly limited to what they can do to the underlying device compared to a program on a computer. That is sort of the basis behind why many claim the Chromebook is safer than a traditional Laptop, because it operates the same way. You can't simply install anything you want on it, you can only install apps from an app store and those apps are limited in what they can do. So while I do believe it's important to have at least some Anti-Virus/Anti-Malware on a traditional PC (even if it's just updated Windows Defender), I don't believe it's really necessary on a phone or a tablet. Nothing is installing itself on these devices, and if you are installing really odd apps from the app store on your own device, then simply uninstall any app that you don't use and/or that might seem suspicious.