The Thirty Meter Telescope (TMT) will provide exciting capabilities for the study of high energy sources of many different types. Future ground based general purpose extremely large telescopes (ELTs) have important roles to play in studies of low mass X-ray binaries (LMXBs) and neutron stars, super novae and gamma-ray bursts (GRBs), super-massive black holes (SMBH) and feedback and other processes in their host galaxies, colliding galaxies and dark matter. From the perspective of TMT, I describe a selection of possible studies that will illustrate the capabilities that the TMT (and the other future ELTs) will provide such as support for ToO observations, time resolved and cadence observations and the importance of coordinated observations with other facilities. I give an overview of the timeline for the beginning of TMT operations and the flexible selection and development process for new instruments.