Insecticides have played a very important role in sustainable production of food, animal feed and also as protection against disease vectors. They act to suppress insect populations and as a consequence of their use, insecticide resistance has evolved. Genetics of resistance include cross and multiple resistance. Cross resistance occurs when a single defence mechanism against one insecticide also confers resistance to other insecticides, even if the insect has not previously been exposed to the latter product and multiple resistance involves multiple, independent resistance mechanisms, which often lead to resistance to chemicals from different groups. Mechanisms of resistance include Preadaptive and Post adaptive strategies. Preadaptation mechanisms include the genetic variations present in the populations and it is chromosomally determined whereas Postadaptive mechanisms include behavioural and physiological resistance. Metabolic resistance is a common defence mechanism, based on enzymatic systems that protect the insect by detoxifying/sequestering insecticide molecules. Enzymes can detoxify xenobiotics into a nontoxic compound and/or into a form more suitable for rapid elimination from the body. Detoxifying enzymes include Carboxyl esterases, Mixed function oxidases (MFO’S), Glutathion-S-transferases (GST) etc., So there is a need to study the overview of insecticide resistance, mechanisms of resistance, metabolic systems involved and factors responsible for insecticide resistance.