This study will test the safety effect of a single dose of the investigational drug IMCgp100 when administered directly into the metastatic melanoma lesion in patients with advanced metastatic melanoma. IMCgp100 is a drug made up of two components. The first is the T cell receptor designed to bind specifically and tightly with protein found at high levels on the surface of melanoma cancer cells and second is an anti-CD3 fragment that is meant to bind to and activate the T cells. There will be two stage dose regimens each enrolling 3 patients. Stage 1 dose will 0.00017 mg IMCgp100 and Stage 2 dose will be 0.0017 mg IMCgp100. Inclusion Criteria: 1. Histologically confirmed dx of advanced unresectable melanoma not requiring immediate treatment and/or in a window between treatments 2. Two or more cutaneous or subcutaneous melanoma metastatic lesions 7 to 15 mm in at least one dimension and amenable to subsequent biopsy 3. Greater or equal to 18 years of age 4. ECOG PS 0-2 5.