\documentclass[letterpaper]{beamer}
\usetheme{Madrid}
\usecolortheme{default}
\usepackage{ifxetex,ifluatex}
\ifxetex
\usepackage{fontspec}
\else
\ifluatex
\usepackage{fontspec}
\else
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{lmodern}
\fi
\fi
\usepackage{hyperref}
\title{Presentation Title}
\author{Author Name}
\date{\today}
\begin{document}
\begin{frame}
\titlepage
\end{frame}
\section{Introduction}
\begin{frame}{Introduction}
This is the introduction slide.
\end{frame}
\section{Main Content}
\begin{frame}{Main Idea 1}
Detail of the main idea or topic.
\end{frame}
\begin{frame}{Main Idea 2}
Further discussion or examples.
\end{frame}
\section{Conclusion}
\begin{frame}{Conclusion}
Key takeaways and summary.
\end{frame}
\section*{References}
\begin{frame}{References / Additional Information}
\begin{thebibliography}{1}
\beamertemplatetextbibitems
\bibitem{example}
Author, \emph{Title}, Source, Year.
\end{thebibliography}
\end{frame}
\end{document}