Metal halide perovskite nanocrystals (NCs) have demonstrated great advances for light-emitting diodes (LEDs) applications, owing to their excellent optical, electrical properties and cost-effective solution-processing potentials. Tremendous progress has been made in perovskite NCs-based LEDs during the past several years, with the external quantum efficiency (EQE) boosted to over 20 %. Recently, metal doping/alloying strategy has been explored to finely tune the optoelectronic properties and enhance material stability of perovskite NCs, leading to further improved device efficiency and stability of the obtained perovskite NCs-based LEDs. In this review, we summarize recent progress on the metal doping/alloying of perovskite NCs and their applications in LEDs. We focus on the effects of different metal doping strategies on the structural and optoelectronic properties of the perovskite NCs. In addition, several works on high-performance LEDs based on metal doped/alloyed perovskite NCs with different light emission colours are highlighted. Finally, we present an outlook on employing metal doping/alloying strategies to further improve the device efficiency and stability of LEDs based on perovskite NCs.