My iMac won’t load past the Apple logo

Follow the steps at > If your Mac starts up to an Apple logo or progress bar - Apple Support

Tip: plug your keyboard into the iMac with the supplied charging cable and then try the startup key commands.

You're welcome.

Yup' the last reference at the very bottom of the support article that I posted.

If your Mac continues to start up to an Apple logo or progress bar, it might need service. Get service.

What you are experiencing is likely a hardware failure. Please take the computer to your local Apple Authorized Service Provider to have it professionally diagnosed. Once you have done that then you can decide if you want to repair or replace.

In the event that you decide to replace (if it’s a 2017 or earlier definitely replace) then you can use your Time Machine backup to migrate from. Instructions for that are in Setup Assistant and Migration Assistant - Apple Community