Lightning has a small chance of melting iron bars

doc/fixes3-7-0.txt

@@ -1273,6 +1273,7 @@ hero had worn amulet of magical breathing become unworn during theft by nymph,
 digging down on a magical trap causes it to explode
 thrown potion of sickness now bypasses target's innate magic resistance but
 	only affects current hit points, no longer also reducing maximum HP
+lightning has a small chance of melting iron bars
 
 
 Fixes to 3.7.0-x General Problems Exposed Via git Repository

src/zap.c

@@ -5143,11 +5143,16 @@ zap_over_floor(
         (void) create_gas_cloud(x, y, 1, 8);
         break;
 
+    case ZT_LIGHTNING:
+        /*FALLTHRU*/
     case ZT_ACID:
         if (lev->typ == IRONBARS) {
+            if (damgtype == ZT_LIGHTNING && rn2(10))
+                break;
             if ((lev->wall_info & W_NONDIGGABLE) != 0) {
                 if (see_it)
-                    Norep("The %s corrode somewhat but remain intact.",
+                    Norep("The %s %s somewhat but remain intact.",
+                          (damgtype == ZT_ACID) ? "corrode" : "melt",
                           defsyms[S_bars].explanation);
                 /* but nothing actually happens... */
             } else {