I want to build a simple test lamp that uses an LED to indicate that a circuit at 24v can supply 5 amps.
I could use a bulb but would prefer to use an LED.
You need a circuit to detect that the 24V has not dropped when it is loaded with a HUGE 4.8 ohms/120W resistor.
Maybe you could use two 12V/60W car headlights in series as the load.
in addition to the load that AG mentioned, the circuit to detect the 24V can be simply a TL431 with resistor divider to provide 2.5V at the reference terminal when 24V is supplied to the circuit. An LED and resistor can then be connected between the cathode and 24V supply.
I hope you won't be testing 24V circuits that aren't intended to provide as much as 5A. The 4.8 Ohm load could well result in release of the magic smoke .