Abbreviated MAPK Targeted Therapy Plus Pembrolizumab in Melanoma

* This research study is a Phase II clinical trial. Phase II clinical trials test the safety and effectiveness of an investigational drug to learn whether the drug works in treating a specific disease. "Investigational" means that the drug is being studied. * The FDA (the U.S. Food and Drug Administration) has approved pembrolizumab, dabrafenib, and trametinib for this specific disease but the combination of all three has not been approved. * This study is being conducted to document whether trametinib with or without dabrafenib taken for brief period of time prior to and with pembrolizumab works better than the investigators expect pembrolizumab to work in participants with unresectable and/or metastatic melanoma. All three of these drugs are FDA-approved for unresectable and/or metastatic melanoma; however, they are not FDA-approved for use all together. * Pembrolizumab is a type of antibody that inhibits the cancer cell growth. An antibody is a cell that attaches to other cells to fight off infection. * Trametinib is a cell inhibitor that binds to the cancer cells to inhibit the cancer cells' signals to decrease cell growth. * Dabrafenib is also a cell inhibitor and works by stopping the cancer cell from duplicating.