Abstract: Metals were first refined 10,000 years ago and have been a crucial component in everything from construction materials to electronic components since. One important property of these metals is their sensitivity towards gas-phase molecules. By constructing metallic nanomaterials and optimizing their surfaces, we can use metals and alloys to build ultrasensitive gas sensors for monitoring the air around us. First, I will investigate ethylene, which is a plant hormone responsible for fruit ripening. By building a single platinum nanowire, we were able to detect ethylene down to single-ppm concentrations. Secondly, I will investigate hydrogen, a fuel source for green vehicles which can turn to an explosive hazard if left unchecked. The addition of a surface alloy allows us to build rapid safety sensors with nanoribbons of palladium metal. I will discuss many of the variables that are investigated in each project, as well as the implications for designing future materials based on the principles discussed here.