Recent advances in understanding how cancer develops and spreads have led to effective new treatments and improved outcomes for patients with melanoma. However, we know that these new treatments do not work for all patients: some do not respond to them and some initially respond but then develop resistance. The overall aim of this study will be to collect tumour biopsies, biomarkers present in the blood, and other biological specimens which can be used to try to understand why resistance to anti-cancer treatment occurs, and to develop predictive biomarkers of this resistance in patients with locally advanced and metastatic malignant melanoma. The study will be open to NHS patients aged 16 and over, who have been diagnosed with advanced melanoma, and who will be receiving treatment for their disease as part of their routine care. Patients will be asked to provide samples from tumour biopsies before, during and after treatment. We will also ask for blood samples to look at biomarkers in the blood and see how these correspond with tumour samples, which will further help us to understand treatment response. Biomarkers are substances in the body that can be measured and help indicate how a disease is developing. It is hoped that soon we will be able to monitor cancer by analysing a patient's blood samples, thus reducing the need for biopsies. As blood tests could be taken more frequently, signs that patients are becoming resistant to treatments could be picked up sooner. As well as monitoring biomarkers, we would also like to understand what happens to the healthy cells surrounding the tumour during treatment. This will improve our understanding of how cells adapt and respond to treatments, and may eventually lead to the discovery of new biomarkers to help predict which patients will develop resistance to certain treatments.