Is it possible to run Windows on an M1 Mac?

Providing you have already paid for the appropriate Windows license, and you want to run it in very slow emulation with a free Virtual Machine, you might want to look into UTM. Otherwise, you will need a subscription for Parallels Desktop 18 or later to run strictly Windows 11 ARM as a virtual machine guest.

Parallels will allow you to run Windows 11 ARM from an external drive location. No experience with UTM, so can't say.

You can only run the ARM64 version of Windows 11 as a virtual machine on Apple silicon Macs.

FWIW, I run the ARM64 version of Windows 11 in Parallels 18 on my M1 MacBook Air and FWIW, it's much faster than Windows on my Asus laptop. It also has zero effect on the Mac when it's not running.

You may want to read this…

Limitations for Windows 11 Arm-based PCs

In some situations, users with Arm-based computers may face issues with Windows 11 due to certain limitations. These limitations are mentioned in a blog post available on the Microsoft website.

• Drivers for hardware, games, and apps will only work if they are developed for Windows 11 Arm-based computers. Hence, if a driver does not work on an Arm-based PC, software or hardware that relies on that driver will also not work.
• The games that require DirectX 12 or OpenGL3.3 or greater will not work.
• Users may experience problems with the apps used to customize the Windows experience, such as cloud storage apps, input method editors, etc.
• Though Windows Security protects users’ systems from all types of threats, users still install different third-party antivirus software. If you have an Arm-based Windows 11 PC, some third-party antivirus can’t be installed.
• Windows Fax and Scan is not available on Arm-based PCs.

Although it is possible to do, I'd highly recommend NOT doing so. If you want to run a Windows 11 machine, just buy a low cost pc that comes with it. Don't ruin your Mac experience by adding a virtual machine of another OS. I've done it....Not worth the degradation and interference to macOS, ruining the overall pleasant mac experience!