How are phosphorus atoms bonded in P4 molecules?

In a $P_4$ molecule, the four phosphorus atoms are arranged in a tetrahedral structure. Each phosphorus atom is joined to the other three atoms by single covalent bonds.1

This configuration is considered relatively unstable or metastable because the formation of these tetrahedra forces the bond angles to be 60°, which deviates significantly from the preferred bond angles of 90° to 109°. Due to this strain and the relatively weak van der Waals forces between separate $P_4$ molecules, white phosphorus is highly reactive and possesses a low melting point.1