Minty said:
1.Does XXX%MF decrease the drop rate of runes?
2.Can XXX%MF insrease the drop rate of charms?
No.
MF increases the chance of an item turning magic/rare/set/unique, but it has NO effect on the items that drop. It also has NO effect on the outcome of variable stats on the item (i.e. if, for example, an amulet drops as Maras, the chance of getting at 30% is the same with 0%MF and with 100000% MF), and NO effect on the mods that appear on a magic/rare item.
This also means that MF has almost no effect on charms at all: charms are always at least magic (just like rings or amulets), so MF has no effect here. There are no rare and set charms, so no effect from MF either. There is *one* random unique charm, Gheeds --- that's the only thing where MF comes into play, as it increases the chance for a grand charm to turn unique --- the other unique charms are fixed drops from certain monsters, so they don't use the normal item generation rules.