Quick Verdict
Corporate bonds are NOT HALAL. A corporate bond is a loan from you to a corporation. The corporation pays you interest for the use of your money. This is riba, regardless of whether the issuing company is otherwise halal or haram.
Does It Matter if the Company Is Halal?
No. Even if Microsoft (a halal company) issues a bond, buying that bond means lending money at interest to Microsoft. The permissibility of the company's business doesn't change the nature of the debt transaction. You're earning riba from Microsoft the same as from JPMorgan Chase.
High-Yield Corporate Bonds
High-yield (junk) bonds are even more clearly problematic — the elevated interest rate reflects higher risk, making it more speculative. Higher risk + interest payment = prohibited under both the riba and gharar principles.
Corporate Bond ETFs
Bond ETFs (BND, LQD, HYG, etc.) are pools of corporate and/or government bonds. All bond ETFs are not halal for Muslim investors as they distribute interest income to shareholders.
Sukuk as the Corporate Bond Alternative
Companies can (and do) issue sukuk as Islamic alternatives to conventional bonds. Malaysia's corporate sukuk market is the largest in the world. Gulf companies including Aramco, Emirates, and many banks issue sukuk. These are the halal way for Muslim investors to participate in corporate debt markets.
Bottom Line
Corporate bonds, regardless of who issues them, are interest-bearing loans and are not permissible for Muslim investors. Sukuk, equity investing, or dividend stocks are the appropriate alternatives.