fact 1: ancient civilization used to live on the island but have disappeared. see the four stone statue and the stonework glimpsed in Ben's secret closet.

fact 2: there is a big monster roaming about the island, that cannot be anything mechanized or biological, but when one character got up close he did see faces/images floating about in it.

fact 3: all the dharma people have fucked off too, except Ben, his former wife - who says 'you have no idea what he is capable of' - and his daughter. infact didn't Ben gas all the dharma people.

anyway, plot of the forbidden planet: ancient civilization once existed on a planet now only inhabited by one man and his wife and daughter. there were other people that arrived with him but they were wiped out by a monster. some newcomers arrive and are also attacked by the monster. but the survivor lets them stay at their own peril, and shows them a secret room behind a bookcase in his study that leads to an underground lab and then to a vast machine created by the ancient civilization. he says this machine lets the mind fabricate physical objects from pure energy, although even with his huge IQ - boosted by one of the alien machines - he, as a human, can only muster a small object like a doll. blablabla monster keeps attacking, the newcomes break into his lab and does the IQ boost and works out that the monster is actually being generated by the survivor's subconscious mind. it is hatred/jealousy/rage/greed manifest. subconscious mind is much more powerful than the conscious.

as for the tempest, well it's quite similar but one important detail was that the survivor was a duke usurped by his brother and sent into exile on an island. he uses newfound magical powers to shipwreck his brother there too and exact revenge on him. whitmore is probably ben's brother, and he's mad that ben kept the island for himself rather than share it with whitmore when they were both in dharma.

so like, most wierd things that happen can be explained by activity of the subconscious mind. clearly anyone on the island to greater and lesser extents interacts with this 'magical' force. ben can summon the smoke monster. walt read about polar bears then one appeared. locke and rose can heal themselves. figures from each person's past can appear on the island. ben wants locke to kill his father, when he refuses he's annoyed because locke has failed to understand that all he'd really be doing was killing off an unhealthy part of his own subconscious.

there's also something about time travel, which will be a distraction for the most part but will probably be used to explain why there are so many strange coincidences in the character's past - again, the subconscious is 'generating' them or something like that