A Beamer font theme represents the style of the font used in the document. Beamer comes with the following predefined font themes:

• default (This is sans serif.)
• professionalfonts
• serif
• structurebold
• structureitalicserif
• strucutresmallcapsserif

To set the font theme for a Beamer document use the \usefonttheme command in the preamble of the document.

For example to set the font to serif:

\usefonttheme{structurebold}