Durvalumab With or Without Metformin in Treating Participants With Head and Neck Squamous Cell Carcinoma

PRIMARY OBJECTIVES: I. To investigate the combined effect of metformin and durvalumab on the immune tumor microenvironment, specifically with respect to alterations in T cell polarization (Th1/Th2 ratio) and tumor associated macrophage (TAM) (M1/M2 ratio) as measured by cytokine shifts in tumor specimens and peripheral blood. SECONDARY OBJECTIVES: I. To investigate the combined effect of metformin and durvalumab on the metabolic microenvironment, specifically with respect to alterations in immunohistochemical markers of the reverse Warburg effect. II. To further characterize the alterations in intratumoral immune cell populations (effector T cells \[Teff\], regulatory T cells \[Tregs\], tumor associated macrophages \[TAMs\], and myeloid-derived suppressor cells \[MDSC\]). III. To assess changes of the intratumoral immunophenotype and metabolism after exposure to durvalumab and metformin by transcriptome analysis using a ribonucleic acid-sequencing (RNA-seq) transcriptome analysis. IV. To assess the efficacy of combined durvalumab and metformin treatment prior to surgery as determined by radiographic response and immune-related response criteria (irRC). V. To assess the safety and tolerability of the combination of metformin and durvalumab.