Most metals are transition metals. They sit in the central block of the periodic table, between Group 2 and Group 3. Iron, copper, nickel and chromium are all examples.
Transition metals share some typical properties. They have high melting points, so almost all of them are solid at room temperature (mercury is a rare exception). Iron melts at about 1538 °C, whereas sodium melts at about 98 °C. They also have high density, so they feel heavy for their size. Their compounds are usually coloured: copper compounds are blue, iron(II) compounds are green and iron(III) compounds are orange-brown. Compounds of Group 1 metals are usually white.
Many transition metals and their compounds are good catalysts. A catalyst speeds up a reaction without being used up. Iron is the catalyst in the Haber process, which makes ammonia.