Explosion welding is a relatively rare welding process, in part due to the awesome fact that in order to do it you need to be an explosives expert! But it’s useful for bonding two large plates of metal together.
One of the coolest things about the explosion welding process is that you can combine materials that can’t normally be welded using other processes. For example, maybe welding copper to steel! These things usually don’t mix.
Here’s a cool little video that shows you how it’s done.