Re: what kind of metals can i
Unless you get/have lots of experience stay away from aluminum. Welding it takes skill and experience not to mention specialized equipment.
That being said I'll suggest you stick with good old steel. As for sticking it together I'll also suggest you buy and get good with a nice little wire feed (MIG) welder. Brazing with an oxy/acetylene torch will work but being proficient at it takes practice and the right materials and again, equipment. The MIG welder can be mastered quickly with practice and will give you strong/safe welds. Before you start building bicycle frames I'd suggest you do some reading on basic metal working. There's more to it than simply cutting and welding things together. You'll probably get several opposing opinions on this; mine is just one.
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