max gate voltage (Vgs) is nothing to do with the load.
The max gate-source voltage is a limit you must observe or you risk instantly blowing the gate oxide,
whether or not there is any load - this is just like overvoltage damage to a capacitor. Once you do this
the gate is no longer isolated from the source and drain and you have a crippled device. If the device is
switching high power gate-oxide failure will then lead to catastrophic failure.
The drain-source max voltage (Vds) is defined as the point where the drain-source leakage current rises above
some nominal point, with the device hard-off (Vgs=0). Some devices can take a certain amount of breakdown
energy if this is exceeded, as used with ignition systems. Too much energy will simply overheat (melt) the
device (or even explode it).
The IRF520 is not logic-level, it needs Vgs >= 10V to turn on (nominally 12V). You've been
sold a lemon.
Logic level devices often have a Vgs requirement of >= 4.5V (nominally 5V).