Metal ions, such as Na+, Mg2+, Ca2+, and Zn2+, are highly abundant in biological systems. For many G protein-coupled receptors (GPCRs), metal ions, especially Na+, have been found to stabilize the receptors' inactivate state preventing receptor activation. Besides this role, recent studies indicated that metal ions can modulate ligand-GPCR interactions allosterically. These findings on ion-mediated GPCR signaling open new vistas for understanding the functioning of GPCRs and further could help in designing potent therapeutic compounds targeting GPCRs. Here we report on recent findings about role of orthosteric and allosteric metal ions in GPCR signaling and drug discovery. This article is categorized under: Structure and Mechanism > Molecular Structures Molecular and Statistical Mechanics > Molecular Mechanics Molecular and Statistical Mechanics > Molecular Interactions