Hi Truong
Thank you for contacting Syncfusion support.
Query 1: how to change icon for minimize, maximize and close button?
At present, there is no option to customize the MetroForm default ControlBox button bounds and appearance. But we can add custom caption images on form caption. please refer the below article that explain how to customize caption buttons as per your requirement.
Query 2: how can i remove margin between control and form ( in this below picture, how can i remove space between panel, which is contains grid grouping control and form)?
In our MetroForm implementation, we have maintained the highlighted white space for the below reasons.
1. To resize the form easily.
2. Displaying the content in the form without cropping at maximized state.
This white space can be hide by setting MetroForm Backcolor same as container control Backcolor. please refer the below documentation,
Please let us know if you require any further assistance on this.
Regards,
Mallika