# [Tex/LaTex] How to boldify math without changing font style

math-mode

I want to boldify math equations and symbols with out changing the actual font.

I tried the following, but I am not getting satisfactory results.

      a=f \equiv 2 \mod 4
\bm{a = f \equiv 2 \mod 4}
\mathbf{a = f \equiv 2 \mod 4}
{\boldmath $a = f \equiv 2 \mod 4$}


The output for the above tags is as follows

I want my equation like the third line with fully bold, but with preserved alphabet font as in line 1.

\bm is not boldifying the entire equation, and \boldmath is not boldyfying at all. How can I preserve alphabet font using \mathbf?

You need \bm or \boldmath, not \mathbf

\documentclass{article}
\usepackage{amsmath}
\usepackage{bm}

\begin{document}

$a=f \equiv 2 \mod 4$

$\bm{ a=f \equiv 2 \mod 4}$

{\boldmath $a=f \equiv 2 \mod 4$}

\end{document}


Of course the bold symbols need to exist, not all font sets include bold.