\documentclass{article}
\usepackage{amsmath,amssymb,amsthm}
\usepackage{fontspec,unicode-math}
\setmainfont{Classical Garamond BT}
%\setmainfont{Elegant Garamond BT}
%\setmainfont{Cormorant Garamond}
\setmathfont{TeX Gyre Pagella Math}

\newtheorem{axiom}{Axiom}
\newtheorem{theorem}[axiom]{Theorem}
\newtheorem{definition}[axiom]{Definition}
\newtheorem{lemma}[axiom]{Lamma}
\newtheorem{example}[axiom]{Example}
\newtheorem{remark}[axiom]{Remark}
\newtheorem{exercise}[axiom]{Exercise}

\title{Article}
\author{Author}
\date{\today}

\begin{document}
\maketitle
\section{Section}
\end{document}