Metal hydrides (FeH, CaH, MgH, ...) and metal oxides (TiO, VO, ...) are the dominant sources of opacity at visible wavelengths in low-mass stars and warm brown dwarfs. In these objects, the presence or absence of metal hydrides and oxides is used to estimate properties such as metallicity, surface gravity, weather, and magnetic field strengths. Hot Jupiters and ultra-hot Jupiters have similar temperatures and so it is expected that these molecules would also be present in their atmospheres. Opacity from metal oxides and hydrides was also predicted to cause the temperature inversions that we see in some ultra-hot Jupiters. However, conclusively detecting any of these species has proven extremely challenging. I will discuss work that I have done to detect FeH in a survey of hot Jupiters observed at high spectral resolution and to place the non-detections into context, both with similar planets observed at low spectral resolution and with brown dwarfs. I will also discuss ongoing work to test high resolution line lists so that we can better search for more metal oxides and hydrides in exoplanet atmospheres.