Since there's allotrope for carbon, I thought there must be allotrope for metal etc.
Guess what? There are allotrope for oxygen, sulphur, silicon, tin and many more.

Allotrope of iron:

Iron represents perhaps the best-known example for allotropy in a metal. There are three allotropic forms of iron, known as alpha, gamma, and delta.
As molten iron cools down it crystallises at 1538°C into its delta allotrope, which has a body-centred cubic (BCC) crystal structure[1]. As it cools further its crystal structure changes to face centred cubic (FCC) at 1394°C, when it is known as gamma-iron, or austenite. At 912°C the crystal structure again becomes BCC as alpha-iron also known as ferrite, is formed, and at 770°C (the Curie point, Tc ) the iron becomes magnetic as alpha-iron, which is also BCC, is formed.

source: http://en.wikipedia.org/wiki/Allotropes_of_iron
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Allotrope of sulphur:

Sulphur is found widely distributed in earth's crust. It is found in vast underground beds of 99.8% pure uncombined sulphur and in many sulphide minerals such as galena,pyrite ,sphalesite and various calcium, magnesium and other sulphates.Sulphur is also present in organic compounds.It is found in animals and vegetables such as onion, garlic, mustard, eggs, proteins etc. Sulphur also occurs along with hydrocarbons such as coal and petroleum.

There are 3 allotropic forms of sulphur:
1)monoclinic
2)plastic
3)rhombic

source: http://www.blurtit.com/q175417.html

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Allotropes of phosphorus: