Inclusion Criteria:

          -  Pathologically confirmed head and neck squamous cell carcinoma (HNSCC), with
             measurable disease by Response Evaluation Criteria in Solid Tumors (RECIST) 1.1

          -  Any stage HNSCC of the 1) oral cavity, 2) oropharynx, 3) larynx, 4) hypopharynx, 5)
             nasal cavity/paranasal sinuses, 6) unknown primary, 7) skin considered to have
             resectable disease. Patients with recurrent disease that is amenable to surgery are
             eligible

          -  Performance status 0-1

          -  Must have a life expectancy of at least 12 weeks as judged by the treating physician

          -  Body weight >30 kg

          -  Absolute neutrophil count 1500/ul or more

          -  Platelets 100,000/ul or more

          -  Hemoglobin 9 g/dl or more

          -  Bilirubin less than or equal to 1.5 x the upper limit of normal (except subjects with
             Gilbert syndrome, who can have total bilirubin <3 mg/dl)

          -  Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) less than or equal
             to 2.5 x the upper limit of normal

          -  Glomerular filtration rate (GFR) greater than or equal to 40 ml/min using the
             Cockcroft-Gault formula or measured creatinine clearance using 24 hours urine
             collection

          -  Women of reproductive potential should have a negative serum or urine pregnancy test
             (minimum sensitivity 25 IU/L or equivalent units of human chorionic gonadotropin
             [HCG]), which must also be confirmed as negative within 28 days of the start of study
             drugs

          -  Women of reproductive potential must use highly effective contraception methods to
             avoid pregnancy for 90 days after the last dose of study drugs. "Women of reproductive
             potential" is defined as any female who has experienced menarche and who has not
             undergone surgical sterilization (hysterectomy or bilateral oophorectomy) or who is
             not postmenopausal. Menopause is defined clinically as 12 months of amenorrhea in a
             woman over 45 in the absence of other biological or physiological causes. In addition,
             women under the age of 55 must have a documented serum follicle stimulating hormone
             (FSH) level less than 40 mIU/mL

          -  Men of reproductive potential who are sexually active with women of reproductive
             potential must use any contraceptive method with a failure rate of less than 1% per
             year. Men who are receiving the study medications will be instructed to adhere to
             contraception for 90 days after the last dose of study drugs. Men who are azoospermic
             do not require contraception

          -  Informed consent: All subjects must be able to comprehend and sign a written informed
             consent document

        Exclusion Criteria:

          -  Patients with nasopharyngeal carcinoma or salivary gland primaries

          -  Any history of a sever hypersensitivity reaction to any monoclonal antibody

          -  Any history of allergy to the study drug components

          -  Any prior history of exposure to an anti PD-L1including durvalumab or PD1-directed
             therapy

          -  Patients who are already taking metformin, or who have taken metformin in the
             preceding 4 weeks

          -  Diabetic patients who are managed by taking metformin or insulin

          -  Major surgical procedure (as defined by the investigator) within 28 days prior to the
             first dose of durvalumab

             * Note: Local surgery of isolated lesions for palliative intent and biopsy procedures
             are acceptable

          -  Subjects who are on medication that are contraindicated with metformin under current
             Food and Drug Administration (FDA) recommendations; current recommendations reflect
             caution when metformin is used with insulin, sulfonylureas, and iodinated contrast dye

          -  Subjects who have received iodinated contrast dye less than 12 hours prior to
             screening meet a temporary exclusion criterion to receive metformin. These patients
             cannot start investigational metformin until 12 hours have elapsed from contrast
             administration. Subjects who are scheduled for iodinated contrast dye are not excluded
             but will be asked to hold their doses prior to dye administration

          -  Mean QT interval corrected for heart rate (QTc) greater than or equal to 470 ms
             calculated from 3 electrocardiograms (EKGs) using Fridericia's Correction

          -  Any concurrent malignancies; exceptions include- basal cell carcinoma of the skin,
             squamous cell carcinoma of the skin of a secondary location, superficial bladder
             cancer or in situ cervical cancer that has undergone potentially curative therapy.
             Patients with a history of other prior malignancy must have been treated with curative
             intent and must have remained disease-free for 2 years post-diagnosis

          -  Any unresolved toxicity National Cancer Institute NCI Common Terminology Criteria for
             Adverse Events (CTCAE) version (v) 5.0 grade >= 2 from previous anticancer therapy
             with the exception of alopecia, vitiligo, and the laboratory values defined in the
             inclusion criteria. Patients with grade >= 2 neuropathy will be evaluated on a
             case-by-case basis after consultation with the Study Physician. Patients with
             irreversible toxicity not reasonably expected to be exacerbated by treatment with
             durvalumab may be included only after consultation with the study physician

          -  Any diagnosis of immunodeficiency or receiving systemic steroid therapy with a dose of
             >10 mg prednisone per day or equivalent or any other form of immunosuppressive therapy
             within 14 days of initiation of therapy, or a prior history of allogenic organ
             transplantation

          -  Active or prior documented autoimmune or inflammatory disorders (including
             inflammatory bowel disease [e.g., colitis or Crohn's disease], diverticulitis [with
             the exception of diverticulosis], systemic lupus erythematosus, Sarcoidosis syndrome,
             or Wegener syndrome [granulomatosis with polyangiitis, Graves' disease, rheumatoid
             arthritis, hypophysitis, uveitis, etc]). The following are exceptions to this
             criterion:

               -  Patients with vitiligo or alopecia

               -  Patients with hypothyroidism (e.g., following Hashimoto syndrome) stable on
                  hormone replacement

               -  Any chronic skin condition that does not require systemic therapy

               -  Patients without active disease in the last 5 years may be included but only
                  after consultation with the study physician

               -  Patients with celiac disease controlled by diet alone

          -  Patients must not be receiving any other investigational agents

          -  Receipt of a live attenuated vaccine within 30 days prior to the first dose of drug on
             trial

          -  Uncontrolled intercurrent illness, including but not limited to, ongoing or active
             infection, symptomatic congestive heart failure, uncontrolled hypertension, unstable
             angina pectoris, cardiac arrhythmia, interstitial lung disease, serious chronic
             gastrointestinal conditions associated with diarrhea, or psychiatric illness/social
             situations that would limit compliance with study requirement, substantially increase
             risk of incurring adverse events (AEs) or compromise the ability of the patient to
             give written informed consent

          -  Patients must not be pregnant or breastfeeding

          -  Active infection including tuberculosis (clinical evaluation that includes clinical
             history, physical examination and radiographic findings, and tuberculosis [TB] testing
             in line with local practice), hepatitis B virus (HBV) (known positive HBV surface
             antigen [HBsAg] result), hepatitis C, or human immunodeficiency virus (positive HIV
             1/2 antibodies). Patients with a past or resolved HBV infection (defined as the
             presence of hepatitis B core antibody [anti-HBc] and absence of HBsAg) are eligible.
             Patients positive for hepatitis C virus (HCV) antibody are eligible only if polymerase
             chain reaction is negative for HCV RNA