Thermite is a mixture of aluminum metal $Al$ and iron(III) oxide. Here is the thermite reaction triggered by the combustion of a magnesium wick.

It is a redox reaction where aluminium is oxidised and iron reduced: $Fe_2O_3$ $+$ $2Al$ $\longrightarrow$ $2Fe$ $+$ $Al_2O_3+$

→   Oxydation states:

The iron product of this reaction is liquid at temperatures produced exceeding $2000^oC$ Fifty years ago, non-welded rail trains caused an unpleasant noise in trains:

The aluminothermy is used to weld railway tracks, thus reducing noise and increasing performance:

Video extracts are due to - the excellent →   Royal Chemical Society - the →   Thermitrex society.

See here the real work:

Video is due to - →   Wolfgang Lendner and Jan Olsson