Welcome to the forums, newcomer!
Make and model of your laptop? You might want to grab a screw driver and try and locate the magnet's located near the hinge area of your laptop's screen where it detects if the lid of the laptop is open or closed. With the laptop lid opened, place the screw driver atop the magnet, then connect to an external display and then press the power button. You should be able to get display to an external monitor/display.
I wrote a guide to a similar issue;
Life ends up dishing out the most unexpected of events. You were just preparing to install Windows on your laptop until someone brushed up against the power brick and snagged the laptop to fall you’re your desk space, corner first onto a hard marbled floor. Now you have a broken screen and you’d...
forums.tomsguide.com
that's how I know of the magnet.