In the US at least a "debt services" default (i.e., you don't make a scheduled payment) is essentially equivalent to a bankruptcy. The debtor has the ability to force you into bankruptcy so companies that are going to miss a payment file for bankruptcy first. This pillages all unsecured debt of the company and annihilates the stock. You should expect the stock to drop to near 0 and anything subordinated to be trading for pennies on the dollar.

Then there is something called "technical default" where a company violates a bond covenant or restructures debt or any number of other possibilities.

A default would devalue bonds since after a default the expected future payments on the bond decline. Also the value of the stock may decline given the enhanced risk of a potential bankruptcy. Stockholder's would have the last rights on any money that remains from paying off debts from the sale of the companies assets upon a liquidation bankruptcy. This would make the values of the shares worthless if there is no money left to claim.