it's impossible to make any decent kind of melt in the microwave
my solution: first toat your slices a little - (toast bagels more cuz they are gummier)
let them cool, then place them in a bag - then put them in the freezer
then microwave the frozen slices - only problem: stuff on top doesn't melt or cook as fast
it's not a perfect solution, but good enough for me
(ps - i don't like toaster ovens so much cuz they can get messy)