We are re-moving an old hot tub from a deck. 220 wire runs from fuse panel under deck. Can we terminate the wire in a closed metal junction box?

I would remove it back to the disconnect/sub-panel and seal the hole.

Unless you are leaving the wire in place for a future hot tub. Then I would just disconnect them from the breaker in the panel and cap them off at both ends.

Yes. You may leave the wires disconnected and capped off inside a metal box. The box must be secured, and must remain accessible. You can not "bury" this box under plaster, or a permanent wall panel or cabinet, etc.