when should i introduce foods to my four month old?

CyLeigh

my baby is 18w and exclusively breastfed. Hes never had any type of formula or cereal. My fiances family really wants me to start him on barley/cereal and maybe even let him try some pureed baby foods. this is my first child and i just wanna do whats best for him, is there anything wrong with led weaning at this point? or even starting him on cereal?