How are sugars metabolized in the body? Are naturally present and added sugars metabolized in the same way?

The digestion of sugars is a well-regulated process. Disaccharides and oligosaccharides are broken down into monosaccharides in the digestive system and these monosaccharides are then absorbed by the small intestine into the bloodstream where they are transported to be used as energy or stored for energy. Glucose taken up by muscle cells in a process mediated through insulin and fructose is largely metabolized in the liver and converted to glucose. 

The human body does not differentiate between sugars naturally present in food or those added to foods and drinks, as they have the same chemical and physical characteristics and are therefore digested in the same way[1].

All sugars, no matter how they started out, eventually end up as monosaccharides like glucose or fructose after digestion.  

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[1] Tappy L, Le KA. 2010. Metabolic Effects of Fructose and the Worldwide Increase in Obesity. Physiol Rev. 90:23-46.