The metals Cobalt (Co) and Nickel (Ni) are common industrial metals which are becoming increasingly prevalent in everyday life. Despite their ubiquity, disruption to homeostasis of trace metals can have severe consequences, as elevated levels of Co2+ and Ni2+ have been associated with various toxic effects. The mechanisms by which metals including Co2+ and Ni2+ exert these effects are not fully understood and may involve various biomolecules. The primary focus of this thesis is on the interactions of Co2+ and Ni2+ with lipid membranes, as disruption to membrane properties may have consequences for transport, signalling, and overall cellular integrity. This study has shown that Co2+ and Ni2+ rigidify membranes containing negatively-charged lipids in both simple and complex model membranes. Additionally, Co2+ and Ni2+ were found to affect respiration and neutral lipid content in the model organism S. cerevisiae, suggesting that both direct and indirect effects on membrane properties may occur.