Multicellular organisms inhabit an environment that includes a mix of essential nutrients and large numbers of potentially harmful microbes. Germline-encoded receptors scan the environment for microbe associated molecular patterns, and, upon engagement, activate powerful defenses to protect the host from infection. At the same time, digestive enzymes and transporter molecules sieve through ingested material for building blocks and energy sources necessary for survival, growth, and reproduction. We tend to view immune responses as a potent array of destructive forces that overwhelm potentially harmful agents. In contrast, we view metabolic processes as essential, constructive elements in the maintenance and propagation of life. However, there is considerable evidence of functional overlap between the two processes, and disruptions to one frequently modify outputs of the other. Studies of immunometabolism, or interactions between immunity and metabolism, have increased in prominence with the discovery of inflammatory components to metabolic diseases such as type two diabetes. In this review, we will focus on contributions of studies with the fruit fly, Drosophila melanogaster, to our understanding of immunometabolism. Drosophila is widely used to study immune signaling, and to understand the regulation of metabolism in vivo, and this insect has considerable potential as a tool to build our understanding of the molecular and cellular bridges that connect immune and metabolic pathways.