During boot mac shows halfway on loading then does not progress

Have you tried booting from an external USB drive that you setup on another Mac? May just be a defective internal hard drive .

I agree! With Mike (@aactech) you need a bootable macOS external drive ideally with the same OS version. Using a second Mac you can make a bootable OS installer USB thumb drive just to boot from and then repair the OS. If that fails to work then theres a deeper issue within the logic board Vs the Drive.

@aactech I was thinking of this however the issue being is I do not have an iMac readily valuable at the moment (needing a new screen after falling off the desk) I know someone with a MacBook. Would it matter if I’m slightly off on the version or dose it have to be exact?

@danj Thanks for the reply, I’ve just posted another message, if the issue isn’t sorted by using an external drive and/or a new drive what could the most likely issue be? I’d presume something with power however I’m new to repairing iMacs so don’t know how to diagnose most hardware issues.

@jacktechrepair - You stated the system gets half way so that would rule-out the power supply. But until you have a bootable drive setup we can’t go deeper. As for which macOS to use, this is an older system so you can’t use the newest. The highest version this series supports is 10.13 High Sierra but if the system is running the older Sierra you need to use it instead as Apple updated the file system in High Sierra and until you get things working you don’t want to mess things up.