The transition metals are the metals that make up groups 3-12 of the periodic table. This region is called the d-block because it corresponds to the d electron sublevels filling. Some of the bettor known metals in this family are gold, silver, platinum, copper, iron, zinc, chronium, nickel, and mercury, which is the only metal that's liquid at atmospheric pressure and temperature. Transition metals are sometimes called the coin metals, as some are used in coins and jewelry.
The transition metals are less reactive than metals in groups 1 and 2, the alkali metals and alkaline earth metals. Some, such as gold and platinum, are very corrosion resistant. Transition metals all form positive ions. Most transition metals form more than one ion, for example copper forms the ions Cu+ and Cu2+.
Transition metals get their name because the d-block forms a transition between the s and p-blocks, or more generally between most of the other metals and the non-metals. Metals are on the left side of the periodic table and non-metals are on the right. On the attached image the transition metals are shown in yellow and labeled. the heavy line that looks like a staircase to the right of the transition metals separates the metals from the non-metals. Elements that fall along this staircase are called metalloids because they have both metallic and non-metallic properties.