I would not expect quantitative production of hydrogen, from water, by aluminum, in a microwave. The word, quantitative, in this sense means that, if some obscure research (or wacky website) has found a few atoms by some mechanism or some unproven theory, I don't believe you'll get enough produced to make it worth talking about for the home user.
Like AWK: says, aluminum's oxide coating protects it from reactions with the weak acidity and alkalinity found in normal foods. And steam doesn't react with aluminum to produce hydrogen, that's magnesium metal that does that.
Furthermore, like AWK: said, generally aluminum foil isn't used in the microwave, it blocks and absorbs microwaves and the food won't cook evenly. Now, many things behave strangely in a microwave -- things that contain water heat up, thing's that don't do not, things that block microwaves, if they have parts pointed up, may cause arcing, and damage the magnetron, or at least, the plastic wall of the microwave between the magnetron and the cooking space.
You can observe this yourself, if you don't care about the potential damage, with flat aluminum foil, aluminum foil bent up, an unwanted CD-ROM or even a grape, split in half. Or you can avoid household damage by browsing the internet for people who've been playing around is such fashion for a while now. But I don't see good support for your hydrogen explosion.
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Topic: Does Al foil produce Hydrogen in Oven? (Read 3331 times)