Trace elements are minerals that the human body needs in very small amounts; however, they are very important for supporting different functions such as immune responses, enzyme activity, and redox balance. These elements, such as zinc, copper, iron, and selenium, can lead to several health problems, including cancer, when they are not properly balanced in the body. This chapter discusses the roles and functions that zinc, copper, iron, and selenium play in the development, diagnosis, and possible treatment of cancer. Also discussed are how these elements affect signaling pathways in the body, how they may serve as cancer biomarkers, and how they are being looked at in cancer therapy, including using nanoparticles and supplementation. Overall, this paper explains how small elements can play big roles in the body and how they may be used to help manage cancer in the future.