Thor, as known from ancient norse texts, had powers that were given to him through the armor he wore. In order to use Mjonlir, he had to have the gauntlets, and inorder for the magic of the gauntlets to work, he had to have the girdle, which combined with his breast plate, gave him powers over the weather (Mjonlir helped in that department as well). Thor himself had little power over lightning and such without those things.
Now we have Ultimate Thor. The most powerful being in Ultimate Marvel as of yet (I am willing to bet that Ultimate Silver Surfer and Ultimate Galactus will be slightly more powerful). He is on a mission to save humanity from itself.
Now according to Thor, his father, Odin gave him this assignment, because in Norse Mythology, Thor was the protector of humans. Now Also according to Ult. Thor, his father sent him in carnite. Which means he was born of a mortal mother to recieve his human body (very much like Jesus).
Now let's say you're a twelve/thirteen year old kid, and you recieve a vision of something from asguard saying that you are the norse god of thunder and you need to save the world. Ah-ha! Here is your nervous breakdown. Under serious pressure to save the world and you 'breakdown'. Now you are released from the hospital and you figure to save the world, you need to go into the medical profession. Here's where Thor becomes a nurse.
Now how exactly his heavenly weapons were given to him, we don't really know. But they were and now Lokli escapes and realises that his sworn enemy is on a mission. Now to foil Thor's plans. In order to do so he wouldn't do it outright he'd go for help. And maybe, oh I don't know... someone whoes head looks like a red skull would want to take out the rest of the team but Thor is too strong so Loki gets the rest of 'em to lock Thor away with out his weapons and oh guess what? Now the Red Skull can complete his task of destroying the Ultimates, like he so desired. Loki is happy, RS is happy. Se where I'm going with this?