number factors make easy state still think important science fiction film ever made despite acting outdated dialogue etcbr br first scale imagination describing krell humanoid race native planet dead  million years advanced earth humansus technology particularly  cubic mile machinebr br second music sound effects inseparable other creates eerie unearthly feeling unlike  traditional classical musicbr br third monster powerful deadly ever envisioned also based real science break laws physics biologybr br finally importantly forbidden planet movie ever made attempts and incredibly succeeds making honest intelligent mercilessly logical statement limits ceiling human or biological entitys development matter long survive speciesbr br in words predicts inevitable destiny