Chemical reactions occur when bonds are broken and rearranged, so the less electrons needing to be rearranged, the faster the reaction. Reactions between ionic bonds require less electron rearrangement so it's more rapid, whereas reactions between covalent bonds require more electron rearrangement so it takes more time and is slower.
Reactions can only be affected in terms of either reaction rate or lowering activation energy by a catalyst. In biochemistry the term used is enzyme.
Some substances are more reactive than others, so it depends on the combination of what types of reactants you are using.