White organic light-emitting diodes (WOLEDs) are promising light-emitting devices. A typical method for generating white light is to superimpose the three primary colours of light - red, green, and blue - or the two colours of light - blue and yellow. These colours are generated from each emitting material doped into the emission layers of the device. To achieve high-quality white light, the emission colours and intensities should be properly adjusted in the device. Apart from the superimposition of colours of light, white light can also be generated by doping with a single molecule that emits visible light in the wavelength range of 380-780 nm. In this review, we have listed some white-light-emitting complexes that are expected to drastically simplify the device fabrication process for OLEDs. We have shed light on these metal complexes and outlined the current status of their synthesis and device applications, looking toward promising future prospects.