Metro belongs to the Wong group and has many branches spread around town. Metro supermarkets are very similar to Wong ones. But generally speaking they offer lower prices and are more orientated towards promoting local products. This makes Metro Super- and Hypermarkets very popular.
If you regularly shop at Metro, you might want to think about getting the "Tarjeta Metro"; it's a credit card issued by Scotiabank. The Tarjeta Metro gives you monthly changing exclusive offers and discounts.
A list of all Metro Supermarkets in Lima and the provinces can be found on their webpage under "Nuestras Tiendas".