I have blank screen upon starting the Mac and it fours not go further though the Backlit is on

I tried all this but no luck I connected to an alternate display device thru HDMI. I could see that logo comes up and then the progress bar starts to load and halfway thru goes blank. The power is still there as I could see the backlit and caps lock green light on

I drained the battery Completely and then restarted the Mac connecting to the power source and it booted. Upon booting it had asked for disabling file vault which i did and complete boot was done.