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Why buy bonds in a no-arbitrage market?
If by "putting money in the bank" you mean regular savings or checking, then the bond locks a rate for a period of time, whereas your savings/checking rate can vary over that period.  That variation might go for you or against you.  Depending on your situation, you might prefer to take a determined rate to the variations.  In addition, some bond types provide tax benefits (e.g. treasuries and municipal bonds) that change the effective return - You cannot just compare the interest rates. Finally, the bonds have "resale" value on the secondary market like stock - Depending on your outlook and strategy, you might by the bond for its value as a security rather than for the interest specifically just like you'd could buy a dividend-paying stock for its value as a security rather than for the dividend.  In other words, you might think that bond values are going up, so you buy bonds with the intent of making a capital gain rather than counting on the interest returned. (The bond market does depend on the interest rate, so these are not independent factors.) I see the other answer that mentions the potential for your bank busting and you losing money beyond the FDIC insurance limit.  The question doesn't specify U.S. Government bonds though, so I don't think that answer is generally good.  It would be good in the case that you had a lot of money (especially an institution or foreign government) and you were specifically interested in U.S. Treasury bonds.  Not so much if you invest in corporate bonds where you have no government insurance / assurance of any sort.  Municipal bounds are also not backed by the U.S. (federal) government, but they may have some backing at the state level, depending on the state.