Explain Ionic Hydrides (Saline Hydrides),Covalent (molecular hydrides),and Metallic (non-stoichiometric hydrides) with examples.

(N/A) Dihydrogen,under certain reaction conditions,combines with almost all elements,except noble gases,to form binary compounds called hydrides. If '$E$' is the symbol of an element,then the hydride can be expressed as $EH_x$ (e.g.,$MgH_2$) or $E_mH_n$ (e.g.,$B_2H_6$).
The hydrides are classified into three categories:
$1.$ Ionic or saline or salt-like hydrides: These are stoichiometric compounds of dihydrogen formed with most of the $s$-block elements which are highly electropositive in character. Example: $NaH$,$CaH_2$.
$2.$ Covalent or molecular hydrides: These are compounds of dihydrogen formed with most of the $p$-block elements. Example: $CH_4$,$NH_3$,$H_2O$,$HF$.
$3.$ Metallic or non-stoichiometric hydrides: These are formed by many $d$-block and $f$-block elements. They are often non-stoichiometric,being deficient in hydrogen. Example: $LaH_{2.87}$,$YbH_{2.55}$.