What can I use to seal a high pressure metal power steering line (big hole)

The only way you have a slight chance of a successful repair is by using a ‘compression union’ - provided one can be found that’s the correct size and the line is straight enough at the damaged section. Any other attempted methods will fail in short order - there’s simply too much pressure - the hose clamps will not hold the hose onto the metal line - fact! The BEST repair is replacement!