Operating in a high temperature and pressure environment is a serious challenge for microelectronics device packaging. This study evaluates the electrical and mechanical behavior of Al, Ag, Mo, Nb and W metallization on ceramic substrates aged under harsh conditions, with the latter three showing great potential as candidates for replacing Cu. In the experiments, metals of interest were deposited by physical vapor deposition on alumina substrates. Samples were aged at 400°C and in 100 MPa argon pressure to simulate the harsh environment condition. During initial aging, it was observed that there was varying degree of electrical resistance changes. It can be understood that metal grains may grow during the initial thermal aging, leading to reductions in electrical resistance of some metals. Such reductions were observed on Ag and W samples. In comparison, there were much smaller increase in the measured resistances of Al and Mo. Nb shows the most significant increase in resistance that practically renders it unsuitable as an interconnect. While Ag shows considerably weak metal-to-substrate adhesion, the other four metals show satisfactory post aging metal-to-substrates adhesion. From these results, considering the physical and electrical properties of the metal, Al, Mo and W could be good candidates for high temperature and pressure applications.