There are several ways the Executive Branch can check the Legislative Branch. The President has the power to veto bills sent to him by Congress. That means he does not sign the bill into law. In the State of the Union Address, the President lays out his legislative agenda and those items are usually addressed first in the new Congress. The President can give speeches and appear on TV and radio to ask the public to support or oppose certain legislation. The right of "executive privilege" or the right to withhold information that Congress may want to obtain from the President gives the executive a way of blocking action and a way of forcing Congress to bargain with him over policies.
The president can veto bills that congress creates.
In order to balance that, congress can override a veto.
In order to keep a balance on both of these, the Supreme Court can declare any law unconstitutional.
The president also appoints the Supreme Court Justices, but congress has to approve of these appointments. So there is another round of checks and balances.
That's a little more than you were asking for I think, but it's a good simple overview of some checks and balances.
They can declare laws unconstitutional and veto them.
President vetos the bill
The executive branch can veto proposed bills made by the legislative branch. This power division is laid out in Article 1, section 7 of the Constitution. This procedure allows the executive branch to have some power over the legislature and thus "check" the legislative branch's power.
The legislature can check the power of the chief executive or president by overriding, approving and impeaching.
Checks and balances - the executive branch can check the power of the legislature though the veto. The legislature can check the power of the president through overriding the veto.
Booty
The other arms of government provide check for executive power. The legislature which makes laws and the judiciary which interprets the law provide a check for executive power.
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The President is the power of the executive branch. He appoints all of the leaders of the 15 departments.