Electrial metrology has undergone a series of profound changes during the last decades and strongly contributed to the 2019 revision of the SI based on a set of seven defining constants. The discovery of the Josephson and quantum Hall effect revolutionised the electrical standards by replacing reliance on material artefacts with constants of physics. This article presents an overview of both quantum effects and their implications on the electrical units and on metrology at large. Aspects of impedance metrology and some specificities of high-frequency metrology are presented along with a short consideration on how it differentiates from low-frequency metrology. Eventually, a few considerations on metrology in electrical power and energy are discussed.