Massive stars are fundamental in almost every aspect of astronomy, however, their formation remains poorly understood. A number of probes have been used to study the process of massive star formation, among them, astrophysical masers. I will review some of the main results that have come from the study of masers in massive star forming regions. In particular, I will summarize our research on formaldehyde masers, which are one of the few maser species that are exclusively associated with massive star formation. The discovery of periodic formaldehyde maser flares, correlated variability with methanol masers, and the implications of these findings on massive star formation will be discussed.