Metformin Combined With Chemotherapy and/or Immunotherapy in Solid Malignancies

The goal of this clinical trial is to evaluate the safety of Metformin alone and in combination with chemotherapy or immunotherapy in patients with solid tumor cancers. The main questions it aims to answer are: * what are the toxicities of metformin at multiple dose levels * what is the maximum tolerated dose of Metformin in combination with chemotherapy or immunotherapy Participants enrolled will be treated with standard of care chemotherapy and/or immunotherapy in accordance to their disease/stage. In addition, participants will take Metformin alone for 14 days in between the first cycle of chemotherapy and the second cycle of chemotherapy to determine tolerability to the Metformin. Participants will then take Metformin daily in combination with the standard of care chemotherapy and/or Immunotherapy from cycle 2 onwards.