The Ryobi whole stud detector can be used to find wood and metal studs and joists behind drywall. It has 7 LED lights to indicate the full stud or joist.
You can use it on drywall upto 1 1/2 inch thick.
There is a sensor to detect and alert you to live wires.
We have more tips in our home improvement book https://amzn.com/B01MRGO8C5