The transition metals take up the central block of the periodic table, and do not have one group. Iron, for example has many different ions: iron(III) has 3 electrons missing from the outer shell and is Fe3+ but you are just as likely to find iron(II).
Properties and use
Titanium (Ti) is a transition metal widely used for its properties. It is strong but relatively light - perfect for use in the manufacture of aircraft.
Copper (Cu) is widely used in making wire, because it is ductile (a property of all transition metals) and conducts electricity very well
Transition metals are also used widely as catalysts, for example, iron is used in the Haber process to produce ammonia.