Which key materials are less apt to retain thermal signatures and why? -metal -rubber -plastic

The difference between materials in relation to the time they retain a thermal signature relates to their ability to conduct and disperse heat. Since metals are generally highly conductive, metals are likely to quickly lose heat once warmed up, and therefore quickly lose their thermal signature. Plastics and rubber are however insulators and do not conduct heat very well at all. They are likely to retain their thermal signatures for longer once exposed to heat.