Need full details, when you say "monitor" are you talking about the laptop screen? Need model/brand of system, if anything happened before the issue started, is the screen black from the time you turn on the laptop? Can you see anything at all on the screen even if faint, try shining a light on the screen. See if the laptop works with an external monitor. If it does, the screen may need to be replaced or possibly the inverter. Inverter is a lot cheaper to buy, so you may want to try that first.