I carry a basic light socket wired to alligator clips and a 200 watt lamp. When I am troubleshooting an electronic circuit, such as a PLC, that blows fuses, I'll connect the lamp across the fuse holder. The impedance of the circuit under test is considerably more than a 200 watt lamp, so if there's still a fault, the lamp will light. When I've solved the problem, the lamp stays off or glows very dim. It saves alot of fuses.
If you put a screw-in fuse in a lampholder and turn on the switch, you'll find out which will blow first, the fuse, or the circuits' protective device. It'll almost always be the fuse.
If you put a lamp in a fuseholder, and nothing in the circuit is on, nothing will happen. If you turn on something with more impedance than the lamp (a radio, for example), the lamp might glow dimly, or not at all, and the load will work ok. If you turn on something with less impedance than the lamp (a toaster, for example) the lamp will burn bright, and the load won't work.
It's a matter of dividing voltage across multiple resistors, (the lamp and the load) but remember, the resistance of an incandescent lamp is much lower when the filament is cold, and rises rapidly as it heats up.