According to About.com expert Dr. Anne Marie Helmenstine, the simplest way to determine if an element is a metal is to see if it appears with the other metals on the periodic table. There are 117 non-theoretical elements on the periodic table, and all but 17 are either metals or metalloids. Scientists also use chemical experiments to determine if a sample of indeterminate nature contains metal ions.
The flame test is a simple laboratory procedure that reveals metal ions in a material sample solution. To perform this test, the researcher dips a long metal instrument into the solution and then places it in an open flame. The BBC explains that the resulting color of the flame provides valuable information about the presence and type of metals in the solution. For example, lithium ions turn the flame red, potassium ions produce a purple flame and barium ions produce a green flame.
According to Home Science Tools, another useful method of metal detection is to test the sample's ability to conduct heat and electricity. All non-metal materials are extremely poor conductors of both. Other physical properties common among metals include ductility and malleability. Transition metals such as gold and silver bend easily when struck with a hammer, but alkali metals such as sodium and potassium have the consistency of cream cheese.
Some metals are highly toxic. Always wear protective gloves when handling unidentified metal specimens.