compound, or alloy characterized by high electrical conductivity. In a metal, atoms readily lose electrons to form positive ions (cations); those ions are surrounded by delocalized electrons, which are responsible for the conductivity. The thus produced solid is held by electrostatic interactions between the ions and the electron cloud, which are called metallic bonds.Definition:-
Metals are sometimes described as an arrangement of positive ions surrounded by a cloud of delocalized electrons. They are one of the three groups of elements as distinguished by their ionization and bonding properties, along with the metalloids and nonmetals. On the periodic table, a diagonal line drawn from boron (B) to polonium (Po) separates the metals from the nonmetals. Most elements on this line are metalloids, sometimes called semi-metals; elements to the lower left are metals; elements to the upper right are nonmetals (see the periodic table showing the metals).
An alternative definition of metal refers to the band theory. If one fills the energy bands of a material with available electrons and ends up with a top band partly filled then the material is a metal. This definition opens up the category for metallic polymers and other organic metals, which have been made by researchers and employed in high-tech devices. These synthetic materials often have the characteristic silvery-grey reflectiveness (luster) of elemental metals.
An alternative definition of metal refers to the band theory. If one fills the energy bands of a material with available electrons and ends up with a top band partly filled then the material is a metal. This definition opens up the category for metallic polymers and other organic metals, which have been made by researchers and employed in high-tech devices. These synthetic materials often have the characteristic silvery-grey reflectiveness (luster) of elemental metals.
Chemical properties:-
Metals are usually inclined to form cations through electron loss,[1] reacting with oxygen in the air to form oxides over changing timescales (iron rusts over years, while potassium burns in seconds). Examples:
4Na + O2 → 2Na2O (sodium oxide)
4Na + O2 → 2Na2O (sodium oxide)
2Ca + O2 → 2CaO (calcium oxide)
4Al + 3O2 → 2Al2O3 (aluminium oxide)
The transition metals (such as iron, copper, zinc, and nickel) take much longer to 
oxidize. Others, like palladium, platinum and gold, do not react with the atmosphere at all. Some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good conductivity for many decades (like aluminium, some steels, and titanium). The oxides of metals are generally basic, as opposed to those of nonmetals, which are acidic.
Painting, anodising or plating metals are good ways to prevent their corrosion. However, a more reactive metal in the electrochemical series must be chosen for coating, especially when chipping of the coating is expected. Water and the two metals form an electrochemical cell, and if the coating is less reactive than the coatee, the coating actually promotes corrosion.
Physical properties:-
Metals in general have high electric, thermal conductivity, luster and density, and the ability to be deformed under stress without cleaving.[1] While there are several metals that have low density, hardness, and melting points, these (the alkali and alkaline earth metals) are extremely reactive, and are rarely encountered in their elemental, metallic form.
Density:-
oxidize. Others, like palladium, platinum and gold, do not react with the atmosphere at all. Some metals form a barrier layer of oxide on their surface which cannot be penetrated by further oxygen molecules and thus retain their shiny appearance and good conductivity for many decades (like aluminium, some steels, and titanium). The oxides of metals are generally basic, as opposed to those of nonmetals, which are acidic.Painting, anodising or plating metals are good ways to prevent their corrosion. However, a more reactive metal in the electrochemical series must be chosen for coating, especially when chipping of the coating is expected. Water and the two metals form an electrochemical cell, and if the coating is less reactive than the coatee, the coating actually promotes corrosion.
Physical properties:-
Metals in general have high electric, thermal conductivity, luster and density, and the ability to be deformed under stress without cleaving.[1] While there are several metals that have low density, hardness, and melting points, these (the alkali and alkaline earth metals) are extremely reactive, and are rarely encountered in their elemental, metallic form.
Density:-
The majority of metals have higher densities than the majority of nonmetals.None
theless, there is wide variation in the densities of metals; lithium is the least dense solid element and osmium is the densest. The metals of groups I A and II A are referred to as the light metals because they are exceptions to this generalization[1]. The high density of most metals is due to the tightly-packed crystal lattice of the metallic structure. The strength of metallic bonds for different metals reaches a maximum around the center of the transition series, as those elements have large amounts of delocalized electrons in a metallic bond. However, other factors (such as atomic radius, nuclear charge, number of bonding orbitals, overlap of orbital energies, and crystal form) are involved as well.
Conductivity:-
theless, there is wide variation in the densities of metals; lithium is the least dense solid element and osmium is the densest. The metals of groups I A and II A are referred to as the light metals because they are exceptions to this generalization[1]. The high density of most metals is due to the tightly-packed crystal lattice of the metallic structure. The strength of metallic bonds for different metals reaches a maximum around the center of the transition series, as those elements have large amounts of delocalized electrons in a metallic bond. However, other factors (such as atomic radius, nuclear charge, number of bonding orbitals, overlap of orbital energies, and crystal form) are involved as well.Conductivity:-
The electrical and thermal conductivity of metals originate from the fact that in the metallic bond, the outer electrons of the metal atoms form a gas of nearly free electrons, moving as an electron gas in a background of positive charge formed by the ion cores. Good mathematical predictions for electrical conductivity, as well as the electrons' contributi
on to the heat capacity and heat conductivity of metals can be calculated from the free electron model, which does not take the detailed structure of the ion lattice into account.
Electric charge:-
When considering the exact band structure and binding energy of a metal, it is necessary to take into account the positive potential caused by the specific arrangement of the ion cores - which is periodic in crystals. The most important consequence of the periodic potential is the formation of a small band gap at the boundary of the brillouin zone. Mathematically, the potential of the ion cores can be treated by various models, the simplest being the nearly-free electron model. 
on to the heat capacity and heat conductivity of metals can be calculated from the free electron model, which does not take the detailed structure of the ion lattice into account.Electric charge:-
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