Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by using high heat to melt the parts together and allowing them to coal causing fusion. The Importance of welding keeps our economy moving. It is the back bone of our world. While we do not always notice every weld under the hood or behind the walls, welding plays an important role in keeping people safe and advancing our quality of life. It was not until the 19th century that welding as we know it, today, was invented.