If you add a lot of solder to a joint, it will wick and the excess will climb along metal using surface tension. You can cut through the solder when cutting th

If you add a lot of solder to a joint, it will wick and the excess will climb along metal using surface tension. You can cut through the solder when cutting the tops of the header pins off, but it's bad to stress the solder itself like this so you need to reheat it with the soldering iron so it relaxes from the physical stress of cutting.