  Gravitational waves (GWs) generate oscillating electromagnetic effects in the
vicinity of external electric and magnetic fields. We discuss this phenomenon
with a particular focus on reinterpreting the results of axion haloscopes based
on lumped-element detectors, which probe GWs in the 100 kHz-100 MHz range.
Measurements from ABRACADABRA and SHAFT already place bounds on GWs, although
the present strain sensitivity is weak. However, we demonstrate that the
sensitivity scaling with the volume of such instruments is significant - faster
than for axions - and so rapid progress will be made in the future. With no
modifications, DMRadio-m$^3$ will have a GW strain sensitivity of $h \sim
10^{-20}$ at 200 MHz. A simple modification of the pickup loop used to readout
the induced magnetic flux can parametrically enhance the GW sensitivity,
particularly at lower frequencies.
