In the on statement, you need to specify the correct column names.
ON leads.ForeignKeyToleads = Products.PrimaryKey
Substitute "ForeignKeyToleads" with the name of the column in the Products table that contains the Product ID, In other words, the column that acts as the Foreign key relationship to the products table.
Substitute "PrimaryKey" With the name of the column in the Products table that contains the product ID. In other words, acts as the primary Key column