Metabolites are the intermediates and products of metabolism. They are usual small molecules and include a huge range of chemical types from amino acids (which make up proteins), carbohydrates (sugars), and steroids to large, complex fatty acids (which make up lipids and form membranes).
METLIN is the Metabolite and Tandem MS Database which provides information on a comprehensive collection of more than 10,000 metabolites [http://www.biocompare.com/Life-Science-News/120817-Expanding-Database-Enables-Discoveries-In-Emerging-Field-Of-Metabolomics/].
Find the major resources on metabolomics. Figure out how to model metabolites and how to integrate the information on all the metabolites in the most efficient way. What is the most suitable unique identifier for metabolites/chemicals?