Number format in matrix, like siunitx

Use a tabular, with \left[ and \right]:

\documentclass[12pt,a4paper]{article}
\usepackage[spanish,es-noshorthands]{babel}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{mathptmx}
\usepackage{siunitx}
\sisetup{per-mode = symbol}
\begin{document}

\begin{equation*}
\left[
  \begin{tabular}{
    @{}
    S[table-format=-4.2]
    S[table-format=-4.2]
    S[table-format=5.2]
    @{}
  }
   4917.02 & -1053.65 &  1053.65 \\
  -1053.65 & 90233.8  & 16791.5 \\
   1053.65 & 16791.5  & 79980.3 \\
  \end{tabular}
\right]
\si{\tonne\per\metre}
\end{equation*}

\end{document}

How about using the siunitx - columns in table and wrap the bmatrix around?

Please choose the appropiate S settings for your needs.

\documentclass[12pt,a4paper]{article}
\usepackage[spanish,es-noshorthands]{babel}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{mathptmx}
\usepackage{siunitx}
\sisetup{per-mode = symbol}
\begin{document}
    \begin{equation*}
    \begin{bmatrix}
      \begin{tabular}{@{}*{3}{S[table-format=6.2]@{}}}
      4917.02 & -1053.65 & 1053.65 \\
     -1053.65 & 90233.8 & 16791.5 \\
      1053.65 & 16791.5 & 79980.3 \\
    \end{tabular}
    \end{bmatrix}\si{\tonne\per\metre}
    \end{equation*}
\end{document}