This study proposes to treat metastatic non-small cell lung cancer (NSCLC) and head/neck squamous cell cancer (HNSCC) patients who are already initiating an immune checkpoint inhibitor (such as Nivolumab, Atezolizumab or Pembrolizumab) for disease treatment as per FDA approved guidelines. In these patients we will deliver a short-course radiation to a single systemic (non-CNS) site within 14 days of receiving the first dose of immune checkpoint inhibitors. This sequence allows radiation to release tumor antigens from immune inaccessible areas such as necrotic tumor or low perfusion to provide a robust anti-tumor immune response with immune checkpoint inhibitors.