Saab 9-3 won't start

I have a 2002 Saab 9-3 with automatic transmission that won’t start. When I turn the key to ON it makes a humming noise and then a click. When I turn it to START it makes no noise and all the lights go out. I’ve tried using both keys and nothing works. Advice??

Put it in neutral and try starting it from there.

Do you have a way to test the battery (voltmeter)?

Does the car and/or its key have a security system and have you tried another key?