To weld is to use intense heat to merge two pieces of metal together. This word refers to other kinds of joining as well. If two companies merge, they’ve been welded.
Have you ever seen someone with a large metal mask and a blowtorch, doing something to pieces of metal? That person — called a welder — was welding, which joins pieces of metal together through heat. Welding is a type of merging, joining, or connecting. The concept also applies to situations that don’t involve metal or flames. You could say a married couple has been welded. This is word for putting things together.