Welding has gained much advancement since 19th century with the variations in its techniques and methods bringing it in modern era as an art to science. Fusion and pressure welding are two main types of welding which are further divided into subcategories. After welding the metal should possess metallurgical capacity, mechanical soundness and good serviceability i.e. capable of performing well in all the conditions. Discussing fusion welding in detail; the base metal is first melted then filler metal may be added and heat is supplied by various means like electric arc, plasma arc, laser and oxyacetylene gas. It involves various methods like welding by weld fluxes, welding through inert gases and vacuum. Fusion welding has many types: Oxyacetylene Cutting/Welding, Shielded Metal Arc (“Stick”), Metal Inert Gas (MIG) and Tungsten Inert Gas (TIG). Each type involves different processes to weld metal by supplying distinct temperatures depending on the metal to weld. Various welding positions are taken into account such as flat, horizontal, vertical and overhead and joints such as butt joint, strap joints, fillet joint, lap joint and corner joint. In the welding process some defects can also occur like inclusions, segregation and porosity whose care should be taken.