Most deli meats come from sectioned and restructured cuts of meat that are bound together using non-meat additives, emulsions, fillers, and usually lots of sodium.
Unless specifically noted, cold cuts are also very likely to contain sodium nitrite, which helps prevent the growth of bacteria but, unfortunately, has also been associated with cancer. Whole cuts of meats or poultry that are cooked and then freshly sliced are much more natural.